PLEASE HELP THIS IS FOR HOMEWORK AND I DON"T KNOW WHAT TO DO.AH

Simplify (a/b - b/a) times (a - a^2/a+b) a - a^2/a=b is a mixed number

There are 15 plates and each plate is either 7 or 12 inches diameter. which systems of equations do you use to find the number of 7 inch plates, x and 12 inch plates, y

You are a clerk at convenience store. a customer owes 11.69 for a bag of potatoes chips. she gives you a five dollar bill. how much change should the customer receive?