#1
{2(3x-2y)+1=7-x
{12(x+y)-15=7x+12y
{6x-4y+x=7-1
{12x+12y-7x-12y=15
{7x-4y=6|*5
{5x+0y=15|*7
-{35x-20y=30
-{35x+0y=105
-20y=-75|:(-20)
y=3,75
5x=15|:5
x=3
{6x/5+y/15=2,3|*30
{x/10-2y/3=1,2|*30
{36x+2y=69|*10
{3x-20y=36
+{360x+20y=690
+{3x-20y=36
363x=726|:363
x=2
6-20y=36
-20y=36-6
-20y=30|:(-20)
y=-1,5