Question

How do I solve x+4y=22
-x+5y=23

Answer 1

x+4y=22
-x+5y=23            (+)
9y=45
y=5

x+4*5=22
x=22-20
x=2

Answer 2

{ x + 4y = 22     ( + x - x = 0 )
{ - x + 5y = 23

4y + 5y = 22 + 23
9y = 45
  y = 45 
         9
  y = 5

x + 4y = 22
x + 4 . 5 = 22
x + 20 = 22
x = 22 - 20
x = 2

S = { 2 , 5 }