SOLUTION: 2x-3y =9 -5x-3y = 30 i know how to solve for x but not for y can u explain how to bring the x back into the equation to get y

Question 24114: 2x-3y =9
-5x-3y = 30
i know how to solve for x but not for y can u explain how to bring the x back into the equation to get y
Answer by rapaljer(4671) (Show Source): You can put this solution on YOUR website!
Did you solve for x and get x= -3? If so, then substitute x =-3 back into one of the equations, either one will do, let's use the first one. This is just BIG TIME SUBSTITUTION!! As they say in that Glade commercial, "PLUG IT IN, PLUG IT IN!!"

2x-3y = 9
2(-3) - 3y = 9
-6 - 3y = 9

Add +6 to each side:
-6+6 -3y = 9+6
-3y = 15
y= -5

Check in the other equation:
-5x - 3y = 30
-5(-3)-3(-5)= 30
15+15= 30
It checks!!

R^2 at SCC
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