Part of the proceeds from a garage sale was $400 worth of $10 and $20 bills. If there were 7 more $10 bills than $20 bills, how many of each bills were there?

1 Answer
Feb 3, 2016

18 $10 bills and 11 $20 bills

Explanation:

Lets say there are x 10 dollar bills and y 20 dollar bills

from the information given

1) 10x + 20y = 400

there are 7 more 10 dollar bills than 20 dollar bills therefore
2) x = y+7

substituting equation 2 into equation 1
10y +70 +20y = 400

rearranging
y=(400-70)/30 = 11

putting the 11 back into equation 2
x = 11+7 = 18

Therefore there are 18 $10 bills and 11 $20 bills