4x=2y4x=x+5.4解得x=1.8 y=3.6
3x等于5.4x等于5.4除以3等于1.82x=yy=2乘以1.8=3.6
x；5,4除3=1.8y；1.8乘2=3.6
2x=y, 当x=5.4, y=10.9
