10/40+(1/40+1/80)(x-10)=1

问题描述:

10/40+(1/40+1/80)(x-10)=1

10/40+(1/40+1/80)(x-10)=1
1/4+3/8(x-10)=1
3/8(x-10)=3/4
x-10=2
x=12