What is math and who invented math

If you are trying to move an attached term across the equal sign (=), what operation would you use to move it?

Arestaurant charges $100 to rent its banquet room for an event. it also charges $15 to serve dinner to each guest. write an equation for the total cost of the banquet room in terms of the number of guests. deine your variables. what is the total cost of the banquet room for 20 guests?

Can someone answer this question for me