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
