(7/10x+70):(3/10x+70)=7:

问题描述:

(7/10x+70):(3/10x+70)=7:

(7/10x+70):(3/10x+70)=7:4
7×(3/10x+70)=4×(7/10x+70)
21/10x+490=14/5x+280
14/5x-21/10x=490-280
7/10x=210
x=300