Solve by the addition method: 2x-5y=18 ,3x+4y=4

2 x - 5 y = 18  / * 4
3 x + 4 y = 4   / * 5  ( we will use the addition method )

 8 x - 20 y = 72
+
15 x + 20 y = 20
 
23 x = 92
x = 92 : 23
x = 4
8 - 5 y = 18
- 5 y = 18 - 8
- 5 y = 10
y = 10  : ( - 5 ) 
y = - 2

( x, y ) = ( 4, - 2 )