Pls help omg im so lost

What is the product? a-3/15a × 5/a-3

Frank has a devised a formula for his catering business that calculates the number of meatballs he needs to prepare. the formula is m=4a+2c, where c=number of children; m=number of meatballs; a=number of adults. how many meatballs are required for a party of 10 adults and 5 children?

Find y to the nearest hundreds place