7 1/4% equals 7.25% and there is your answer.
68 divided by 85 multiply by 100
68/85=0.8 x 100= 80%
The answer would be c) 129
So since the formula for the sum of a polygon's interior angles is (n-2)180, just make that equal to 2520 and solve for n, which is the number of sides.
STEPS:
1) (n-2)180 = 2520
2) n-2 = 2520/180
3) n-2 = 14
4) n = 16
So the polygon must have 16 sides
This woud be Seven(x) cubed minus 1.