Well first you want to find out how much he weighed after his diet.
140-15= 125
Next you want to take that and divide it by 140
125/140= 0.8928571
To make it a percent multiply by 100
0.8928571*100= 89.28571
Subtract from 100
100-89.28571= 10.71249
He had a 10.71249% decrease in weight
