-77.27% is the change from 66 to 15
Calculation steps:
[( 15 - 66 ) ÷ 66] x 100 = -77.27%
Formula
Percentage change = [(15 - 66) / 66] x 100
Subtract the new number by the original number
15 - 66 = -51
-51 ÷ 66 = -0.7727272727272727
-0.7727272727272727 x 100 = -77.27%