SOLUTION: Help me solve this by the substitution method: 9m+n=80 m-3n=12

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Question 536731: Help me solve this by the substitution method: 9m+n=80
m-3n=12
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
1 x -3 y = 12 .............1
1 y = 80 -9 x ---------2
/ 1 =
y = 80 -9 x
Substitute y in (1)
1 x -3 ( 80 -9 x ) = 12
1 x -240 + 27 x = 12
1 x + 27 x = 12 240
28 x = 252
/ 28
x= 9
Plug the value of x in (1)
1 x -3 y = 12
1 * 9 -3 y = 12
9 -3 y = 12
-3 y = 3
/ -3
y= -1
m.ananth@hotmail.ca