Do not be surprised if a friend of yours solved the same problem differently. Second, when translating a word problem into the language of mathematics, it's quite normal to get more than 1 variable or more than 1 equation. When more than 1 equation results, the equations are called simultaneous and we talk of a system of simultaneous equations. To solve such a system is to obtain values for all variables involved. We'll tackle simultaneous equations on a separate page.
Many formulations are possible for a single problem.
Alexander Bogomolny 2409803 .