-3.25% is the change from 400 to 387
Calculation steps:
[( 387 - 400 ) ÷ 400] x 100 = -3.25%
Formula
Percentage change = [(387 - 400) / 400] x 100
Subtract the new number by the original number
387 - 400 = -13
-13 ÷ 400 = -0.0325
-0.0325 x 100 = -3.25%