Question

{X+2y= 7
{X-2y= -5


{X-y= 6
{X+y= -7

Answer 1

{x+2y= 7
{x-2y= -5
---------
2x= 2
x= 2/2
x= 1


{x-y= 6
{x+y= -7
--------
2x = -1
x= -1/2

Answer 2

a) x+2y=7     1+2y=7
    x-2y=-5    2y=7-1
    2x=2         2y=6
    x=2/2        y=6/2
    x=1           y=3

b) x-y=6         x+1(-13/2)=-7
    x+y=-7       x-13/2=-7
    x=6+y        x/1-13/2=-7/1
    6+y+y=-7   2x-13=-14
    2y=-7-6      2x=-14+13
    2y=-13       2x=-1
    y=-13/2      x=-1/2