2[(60-x)÷60]=1×[(120-x)÷120]

问题描述:

2[(60-x)÷60]=1×[(120-x)÷120]

2[(60-x)÷60]=1×[(120-x)÷120] 两边乘120
4(60-x)=120-x
240-4x=120-x
4x-x=240-120
3x=120
x=40