Basta calcular regra de tres:
8.000 ------------ 100%
x ------------ 125%
100x = 125*8000
100x = 1000000
x = 1000000/100
x = 10.000 e o valor de 125% talque somando temos 18.000
50.000 -------------- 100%
x -------------- 0,4%
100x = 50000*0,4
100x = 20000
x = 20000/100
x = 200
40000 -------------- 100%
x -------------- 1,2%
100x = 40000*1,2
100x = 48000
x = 48000/100
x = 480.
400 -------------- 100%
x -------------- 3%
100x = 400*3
100x = 1200
x = 1200/100
x = 12.
8.600 ------------- 100%
x ------------- 18%
100x = 8600*18
100x = 154800
x = 154800/100
x = 1548.