So in this one, we are DECREASING by 25%, so we say 25% of 820...
25% × 820 =
.25 × 820 = 205
Now since we are decreasing by 25%, we take our answer and subtract it from the original amount, 820.
820 - 205 = 615
820 decreased by 25% is
615.
Try this solution, note, the suggested option is not the shortest way.
Polynomial with real coefficients always has even number of complex roots. We know that one of them is 2 + 5i so the second one will be 2 - 5i and:

Answer B.
The answer is 4605 feet since 921 • 5 is 4605. There are 5 sides and each side 921 so 921 • 5 = 4605 would be the answer