(x+2y)等于5m 式子左右两边同时乘以5/3,即5/3(x+2y)等于25/3m
x-y等于9m式子两边同时乘以4/3,即4/3(x-y)等于12m
5/3(x+2y)加上4/3(x-y)=3x+2y
所以25/3m+12m=17
所以M=51/61
(x+2y)等于5m 式子左右两边同时乘以5/3,即5/3(x+2y)等于25/3m
x-y等于9m式子两边同时乘以4/3,即4/3(x-y)等于12m
5/3(x+2y)加上4/3(x-y)=3x+2y
所以25/3m+12m=17
所以M=51/61