3(x+y)-2(x-y)=28

Let x+y = a and x-y = b.

Original title:

A/3+B/2=6 2A+3B=36 ( 1)

3A-2B=28 (2)

( 1)*2+(2)*3:

4A+6B+9A-6B=36*2+28*3

13A= 156

A= 12, substituting (1):

2* 12+3B=36

3B= 12

B=4

So: x+y= 12 (3)

x-y=4 (4)

(3)+(4):

2x= 16

x=8

(3)-(4):

2y=8

y=4

So the solution set is:

x=8

y=4