Cities are multifunctional by definition, and an increasingly significant function is the tourist function. City tourism is one of the most dynamically developing forms of tourism. Tourists’ decisions regarding choosing a destination are influenced by a number of factors determining the subjective assessment of the tourist attractiveness of a given city, and one of them may be the state of air pollution, as it can have a negative impact on the health of both city dwellers and tourists. This article is an attempt to determine whether potential tourists consider information about the level of a city’s air quality in the assessment of its tourist attractiveness and the impact of this information on their travel decisions. The article presents the results of surveys conducted among a group of 509 respondents from Poland. On this basis, an assessment was made of the extent to which information on the condition of air quality in a given city is relevant for persons planning a tourist trip. In the conducted research, decisions regarding both business and private trips were evaluated. In addition, information on factors that could increase the respondents’ interest in the condition of air quality in the city of the intended trip (e.g., trip with children, trip length) was collected. Due to the fact that tourism is a significant source of income for many cities, the research results presented in the article may be of significant importance for entities creating the urban tourist product and responsible for its management. The article also draws attention to the fact that reducing pollution in cities can contribute to increases in their tourist attractiveness.

For many scientists interval arithmetic (IA, I arithmetic) seems to be easy and simple. However, this is not true. Interval arithmetic is complicated. This is confirmed by the fact that, for years, new, alternative versions of this arithmetic have been created and published. These new versions tried to remove shortcomings and weaknesses of previously proposed options of the arithmetic, which decreased the prestige not only of interval arithmetic itself, but also of fuzzy arithmetic, which, to a great extent, is based on it. In our opinion, the main reason for the observed shortcomings of the present IA is the assumption that the direct result of arithmetic operations on intervals is also an interval. However, the interval is not a direct result but only a simplified representative (indicator) of the result. This hypothesis seems surprising, but investigations prove that it is true. The paper shows what conditions should be satisfied by the result of interval arithmetic operations to call it a “result”, how great its dimensionality is, how to perform arithmetic operations and solve equations. Examples illustrate the proposed method of interval computations.

The paper presents a method for solving real fuzzy systems of linear equations with the usage of horizontal fuzzy numbers (HFNs). Based on the multidimensional RDM interval arithmetic and a fuzzy number in a parametric form, the definition of a horizontal fuzzy number with nonlinear left and right borders was given. Additionally, the paper presents the properties of basic algebraic operations on these numbers. The usage of horizontal fuzzy numbers with linear and nonlinear borders was illustrated in the examples with \(n \times n \) fuzzy linear systems. The obtained results are multidimensional and satisfy the fuzzy linear systems. Calculated solutions of fuzzy linear systems were compared with the results of other methods. The solution obtained with horizontal fuzzy numbers satisfies any equivalent form of fuzzy linear system, whereas the results of existing methods do not satisfy the equivalent forms of the system. The presented examples also show that the method with HFN delivers a full multidimensional solution (direct solution). The analyzed results of standard methods, which are only a part of span (indicator, indirect solution) of a full solution and/or include values that do not satisfy the fuzzy linear systems, are underestimated or overestimated. The proposed method gives a possibility to obtain a crisp solution together with a crisp system of equations; other methods do not possess these properties.

The armed conflict in Ukraine has caused a lot of emotions around the world. Many countries have been involved in helping brutally attacked people, especially mothers and children. The versatile involvement of large powers is monitored and noticeable by the media. Active help from Poland is a very visible sign of human solidarity with the suffering Ukrainian nation. Open hearts, houses and institutions and humanitarian and medical aid are elements of Polish kindness and empathy. The aim of the research was to collect Poles’ opinions about the need to provide humanitarian aid to Ukrainians from the territories of the Russian–Ukrainian war. Capturing feelings of Poles towards Ukrainians during the war is an interesting issue that shows subjective opinions about the existential situation perceived in the space of mutual personal interactions. The results showing opinions on help were collected from a group of 1012 people throughout Poland with the help of an authorial questionnaire. The obtained data shows a positive attitude of Poles to Ukrainians. The most willing to help are people over 49 years old, more often with a good and very good financial situation. Respondents believe that general assistance from other countries and the European Parliament is not sufficient. Military support is accepted the most by the oldest participants of research, and less by the age group up to 30 years who support medical help more. More concerned about the ongoing conflict are respondents under the age of 30 and the least wealthy, including, more often, women. The richest respondents are least afraid of the effects of the ongoing Russian–Ukrainian conflict. The conducted research confirms the openness of Polish society to refugees and brings opinions about existential solidarity with the suffering Ukrainian nation.