-18.52% is the change from 81 to 66
Calculation steps:
[( 66 - 81 ) ÷ 81] x 100 = -18.52%
Formula
Percentage change = [(66 - 81) / 81] x 100
Subtract the new number by the original number
66 - 81 = -15
-15 ÷ 81 = -0.18518518518518517
-0.18518518518518517 x 100 = -18.52%