Story problem to represent 3divided by 1/2

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15

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?

X-10/4 when x = –18 a 7 b –2 c –7 d 2