A student has some? $1 and? $5 bills in his wallet. He has a total of 12 bills that are worth?$40. How many of each type of bill does he? have?

X will be the amount of 1 dollar bill and y the 5 dollar bill

x1 + y5 = 40

x + y = 12

(I'm going to solve for x first, so multiply the bottom equation by negative 5)

x1 + y5=40

x-5+y-5 = - 60

(cross out the y and solve)

x-4 = - 20

(divide)

x = 5

(place it in the equation you didn't use)

5 + y = 12

y = 7

he has 7 fives and 5 ones