Hey guys, I am having trouble with some homework in finishing up these questions. Please help, thanks

In an auditorium there are 4xrows, and each row can accommodate 5yzbenches. Ifxstudents can be accommodated in each bench, then how many students can sit in the auditorium?

Tom and David have 480 marbles between them. Tom arranges them in columns with 6 in each column, and David arranges them with 9 in each column. The total number of columns is 72. Express the above information in the form of an algebraic equation.

The answers don't necessarily have to be numeric, just an algebraic expression is enough. Thanks everyone for taking a look and helping me. I'll be returning the help whenever I can, thanks.