-41.3% is the change from 138 to 81
Calculation steps:
[( 81 - 138 ) ÷ 138] x 100 = -41.3%
Formula
Percentage change = [(81 - 138) / 138] x 100
Subtract the new number by the original number
81 - 138 = -57
-57 ÷ 138 = -0.41304347826086957
-0.41304347826086957 x 100 = -41.3%