Given:
x = candy selling at 6 per pound
y = candy selling at 9 per pound
x + y = 15
6x + 9y = 15(7)
6x + 9y = 105
x = 15 - y
6(15-y) + 9y = 105
90 - 6y + 9y = 105
3y = 105 - 90
3y = 15
3y/3 = 15/3
y = 5
There should be 5 pounds of more expensive candy.
x = 15 - y
x = 15 - 5
x =10
There should be 10 pounds of less expensive candy.
