Answer:
x = 3
Explanation:
Take the first equation- x + 2y = (-1)
Multiply both sides by 2
2(x + 2y) = 2(-1)
2x + 4y = -2
Add first and second equations
(2x + 4y = -2)
+(4x -4y = 20)
= 6x = 18
x = 18/6
x= 3
Extra info- This method is also called as Elimination method in which Elimination (whether by addition of equations or subtraction) of any variable is done.
Hope it helps