Can someone solve this and tell me how they did it? the difference between a number and twenty is equal to the product of five and a number.

This is so hard and it’s for a test

Hamburger heaven is having a lunch special where customers buy one -pound cheeseburger and get one free. if they set aside pounds of meat, how many -pound cheeseburgers can they make?

Allen wants to buy a hover board that sells for $249.99 and a helmet that is $36.54. how much change will allen receive if he gives the cashier three $100.00 bills?