SOLUTION: Use the substitution method to solve the system of equations. Please show all work! m - n = 7; 3m + 2n = 6

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Question 862048: Use the substitution method to solve the system of equations. Please show all work!
m - n = 7;
3m + 2n = 6
Answer by Help Math(4) About Me  (Show Source):
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m - n = 7 (1)
3m + 2n = 6 (2)
solve for m from (1)
m=7+n (3)
now substitute (3) into (2) for m
3(7+n)+2n=6
21+3n+2n=6
21+5n=6
5n=6-21
n=-15/4
n=-3

no plug n=-3 into (1)
m - (-3) = 7
m=4