This article presents the generalization of Zadeh’s extension principle for arithmetic operations on interactive fuzzy variables. Typical kinds of interactivity between financial analyses parameters in industrial enterprises are discussed later. These interactions make use of nonlinear programming methods necessary to calculate the values of selected financial indices expressed by the fuzzy numbers. The article presents the problem of nonlinear programming applied to calculating the values of these indices. Application of the fuzzy model simulation method is also proposed for executing the arithmetic operations on interactive fuzzy numbers. Also, an example of calculating the gross profit for two metallurgical companies is shown.