x/2+y=1 ① ④⑤⑥
x/2-1/3y=-1②
①-②得：y+1/3y=2.4y/3=2.4y=6.y=3/2.代入①,x/2+3/2=1,x+3=2, x=-1
x=-1
y=3/2
3m-n=1①,
3m+2n=16②
②-①得：3n=15.n=5.代入①,3m-5=1, 3m=6, m=2.
m=2
n=5
3m+2n=2①,
2m-n=2②
②x2+①得：7m=6...m=6/7.代入②,2x6/7-n=2, 12-7n=14, n=-2/7
m=6/7
n=-2/7
4/5x-3/4y=1①,
4x-3y+1=0②
①x5-②得：-3y/4=6...3y=-24.y=-8,代入②,4x+24+1=0, 4x=-25, x=-25/4.
x=-25/4
y=-8
3y=x-(x-1)/3①,.3y=(2x+1)/3③
3y=(x+2)/6+2②
③-②得：(2x+1)/3-(x+2)/6-2=0,.2(2x+1)-(x+2)-12=0,.4x+2-x-2-12=0, x=4.代入③,
3y=(2x4+1)/3=3,.y=1
x=4
y=1
5x+2y=25,
3x+4y=15
①x2-②得：7x=35,..x=5,代入②,15+4y=15,...4y=0,..y=0.
x=5
y=0
3(x-1)=4(y-4).4y-3x=13①
2(y-1)=5(x+3).2y-5x=17.4y-10x=34②
①-②得：7x=-21, x=-3,代入①,4y+9=13, 4y=4, y=1
x=-3
y=1