Help in writing a pseudocode for a problem

I started practicing coding problems from the book “Looking for the Challenges #2” and got stuck on first problem. I have read the solution but not able to understand and write a pseudocode for that problem. Please help to make me understand the problem in simpler language

Problem Name : Arithmetic Rectangle
Problem Link : Arithmetic Rectangle

Make sure to let us know what part of the solution doesn’t make sense to you instead of simply saying “I need help on this problem.” If you really don’t understand any part of the solution, that’s fine – you should specify this in your question.