1)10x+13y=-193
4x-5y=35
5y=4x-35 => y=4\5x-7
10x+10/4x-91=-193
40x+10x-364=-772
50x=-408
x=-8.16
y=-13.528
2) 2x+5y=1
4x+3y=9
2x=1-5y => x=1/2-5/2y
2-10y+3y=9
-7y=7
y=-1
x=3
3) 6x+5y=-8
4x+7y=2
4x=2-7y x=> 1/2-7/2y
3-21y+5y=-8
-16y=-11
y=0.6875
x=-19.0625