In parallelogram WXYZ, what is CY?

11ft

15ft

21ft

23ft

The correct answer is 11 ft.

Explanation:

The diagonals of a parallelogram bisect each other. This means that the portion marked x+4 is the same length as the portion marked 2x-7; this gives us the equation x+4=2x-7.

Subtract x from each side:

x+4-x=2x-7-x

4=x-7.

Add 7 to both sides:

4+7=x-7+7

so x=11