(x+y)^(1/3)=-2;
x+y=-8;
(x-2y)^(1/2)=3;
x-2y=9;
y+2y=-17;
y=-17/3;
x=-7/3;
3x-6y=-7-(-34)=-7+34=27;
如果本题有什么不明白可以追问,