SOLUTION: how to do substitution and try to get one solution x+3y=12 x-y=8

Algebra ->  Coordinate-system -> SOLUTION: how to do substitution and try to get one solution x+3y=12 x-y=8      Log On


   

Question 235792: how to do substitution and try to get one solution x+3y=12 x-y=8
Answer by Stitch(470) About Me  (Show Source):
You can put this solution on YOUR website!
Given:
Equation 1: X%2B3Y=12
Equation 2: X-Y=8
---------------------------
Solution:
First solve equation 2 for one of teh variables, I picked X.
X-Y=8 Add Y to both sides
X+=+8%2BY
Now plug (8 + Y) into equation 1 for X
X%2B3Y=12
%288+%2B+Y%29%2B3Y+=+12 Combine like terms
8+%2B+4Y+=+12 Subtract 8 from both sides
4Y+=+4 Divide both sides by 4
Y+=+1
Now plug 1 into equation 2 for Y to find X
X-Y=8
X-1=8 Add 1 to both sides
X+=+9
---------------------------
Check your answer:
Using plug Y = 1 & X = 9 into equation 1
X%2B3Y=12
9+%2B+3%2A1+=+12 Simplify
9+%2B+3+=+12
12+=+12