77.78%
1) Considering that this rectangle is made up of 18 squares
2) Then we can solve it by setting a proportion:
18 --------------- 100%
14 ---------------- x
Cross multiplying it, since it is a proportion we have:
18x = 1400 Divide both sides by 32
x =77.78
3) So we can say that the shaded squares represent 77.78% of the rectangle.