x比y等于3比4,30+x比50+y等于5比7,求x和y

问题描述:

x比y等于3比4,30+x比50+y等于5比7,求x和y

由题得,4x=3y ①
3×(30+x)/3×(50+y)=(90+3x)/(150+3y)=5/7②
①代入②中得
(90+3x)/(150+4x)=5/7
解得x=120
∴y=160