help solving the system? how?

x -y=8
2x +y=7
----------------[adding]
3x=15
=>x=15/3
=>x=5

Now, 5 - y=8
=>-y=8 - 5
=> -y =-3
=>y=3
So, The solutions are:
x=5,y=3 <==ANSWER

3x = 15
x = 5

10 + y = 7
y = - 3

x = 5 , y = - 3

x - y = 8 (solve by using substitution)
2x + y = 7

x - y = 8
x = 8 + y
2x = 2(8 + y)

2x + y = 7
2(8 + y) + y = 7
16 + 2y + y = 7
2y + y = 7 - 16
3y = -9
y = -9/3
y = -3

x - y = 8
x - (-3) = 8
x + 3 = 8
x = 8 - 3
x = 5

∴ x = 5 , y = -3

x = 8 + y

2(8 + y) + y = 7

16 + 2y + y = 7

16 + 3y = 7

3y = -9

y = -3

x = 8 + (-3)

x = 5

3x = 15
x = 5

5 - y = 8
-y = 3
y = -3

(5, -3)

x - y = 8
2x + y = 7
use substi

x = 8 + y
------------------------
2x + y = 7
2(8+y) + y = 7
16 + 2y + y = 7
16 + 3y = 7
3y = 7 - 16
y = -9/3
y = -3

x = 8 + y
= 8 + (-3)
= 5

ok...