若7x+6(x-y)=-4,3x-4(y-x)=18,则x-y=__

问题描述:

若7x+6(x-y)=-4,3x-4(y-x)=18,则x-y=__

7x+6(x-y)=-4 (1)
3x-4(y-x)=18
则3x+4(x-y)=18 (2)
(2)×7-(1)×3
28(x-y)-18(x-y)=126+12
10(x-y)=138
x-y=13.8