(90-X)\(100-X)=80% 怎么解
问题描述:
(90-X)\(100-X)=80% 怎么解
答
(90-X)\(100-X)=80%
90-x=0.8(100-x)
90-x=80-0.8x
x-0.8x=90-80
0.2x=10
x=50