-19.05% is the change from 21 to 17
Calculation steps:
[( 17 - 21 ) ÷ 21] x 100 = -19.05%
Formula
Percentage change = [(17 - 21) / 21] x 100
Subtract the new number by the original number
17 - 21 = -4
-4 ÷ 21 = -0.19047619047619047
-0.19047619047619047 x 100 = -19.05%