-78.57% is the change from 70 to 15
Calculation steps:
[( 15 - 70 ) ÷ 70] x 100 = -78.57%
Formula
Percentage change = [(15 - 70) / 70] x 100
Subtract the new number by the original number
15 - 70 = -55
-55 ÷ 70 = -0.7857142857142857
-0.7857142857142857 x 100 = -78.57%