SOLUTION: Solve the system by the substitution method. x - 3y = 25 -6x - 4y =-18

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Question 34229This question is from textbook Prealgebra & Introductory Algebra
: Solve the system by the substitution method.


x - 3y = 25
-6x - 4y =-18 This question is from textbook Prealgebra & Introductory Algebra

Answer by kietra(57) About Me  (Show Source):
You can put this solution on YOUR website!
[1] x - 3y = 25
[2] -6x - 4y =-18
Use the first equation and solve for x:
[1] x = 3y + 25
Then take what x equals in the first equation and substitute it for x in [2]:
-6x - 4y =-18
-6(3y + 25) -4y = -18
Now solve that equation for y.
-6(3y + 25) -4y = -18
-18y - 150 - 4y = -18
-22y = 132
y = -6
Take that y = -6 and put it back into [1].
x = 3y + 25
x = 3(-6) + 25
x = -18 + 25
x= 7
Always check both solutions in both equations:
[1] 7 - 3(-6) = 25 7+ 18=25 CHECK
[2] -6(7) - 4(-6)=-18 -42 + 24 = =18 CHECK
x= 7, y=-6