-70% is the change from 300 to 90
Calculation steps:
[( 90 - 300 ) ÷ 300] x 100 = -70%
Formula
Percentage change = [(90 - 300) / 300] x 100
Subtract the new number by the original number
90 - 300 = -210
-210 ÷ 300 = -0.7
-0.7 x 100 = -70%
Example