Question 332515
4x+3y= 87>>>>>...1
2x-y= 21>>>>>>...2
..
multiply equation 2 by 2
4x-2y=42
..
(4x+3y)-(4x-2y)=87-42
4x+3y-4x+2y=45
5y=45
divide by 5
5y/5 = 45/5
y=9
..
2x-y=21
plug the value of y in the equation
2x-9=21
add 9 
2x-9+9=21+9
2x=30
divide by 2
2x/2 = 30/2
x=15