1:x=3Y/2,3(3Y/2)+4Y-2=0,Y=4/17,x=6/17
2: x=(8+2y)/3, 2(8+2y/3)+3y=1,y=1,x=2
3: y=2/3-7x,2x+3(2/3-7x)=-5/7,x=1/7,y=-1/3
4: M-2N=8,4*8+N=1,N=-31,M=54
5:4(m+n)/12 -3(m-n)/12=(m+7n)/12
6:5x-2(x+3/2)=2 x=5/4,y=17/8
7:y=4x-13 2x+3(4x-13 )=13 x=13 y=39
8:200