Question

A library has 142 CDs on its shelves. There are 11 shelves that have 8 CDs on each shelf. The rest of the shelves have 6 CDs on each shelf. How many shelves have 6 CDs?

Answer 1

11x8=88
142-88=54
54 divided by 6 is 9
So 9 is the answer.

Answer 2

11(8) + 6x = 142
88 + 6x = 142
Subtract 88 from both sides
6x = 54
Divide both sides by 6
x = 9
9 shelves have 6 CD's