解下列方程组3x-4y=3 2x+3y=19

3x-4y=3 (1)
2x+3y=19 (2)
(1)*3+(2)*4
9x-12y+8x+12y=9+76
17x=85
x=5
代入(1)
15-4y=3
4y=12
y=3
所以x=5,y=3
x/3+y/4=7 (1)
x/4-y/3=3 (2)
两边都乘12
4x+3y=84 (3)
3x-4y=36 (4)
(3)*4+(4)*3
16x+12y+9x-12y=336+108
25x=444
x=444/25
代入(1)
(444/25)/3+y/4=7
y/4=27/25
y=108/25
所以x=444/25,y=108/25