SOLUTION: solve by subsititution method 9m+n=77 m-3n=21

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Question 221134: solve by subsititution method 9m+n=77 m-3n=21
Found 2 solutions by drj, MathTherapy:
Answer by drj(1380) About Me  (Show Source):
You can put this solution on YOUR website!
Solve by substitution method

9m+n=77
m-3n=21

Solved by pluggable solver: SOLVE linear system by SUBSTITUTION
Solve:
+system%28+%0D%0A++++9%5Cm+%2B+1%5Cn+=+77%2C%0D%0A++++1%5Cm+%2B+-3%5Cn+=+21+%29%0D%0A++We'll use substitution. After moving 1*n to the right, we get:
9%2Am+=+77+-+1%2An, or m+=+77%2F9+-+1%2An%2F9. Substitute that
into another equation:
1%2A%2877%2F9+-+1%2An%2F9%29+%2B+-3%5Cn+=+21 and simplify: So, we know that n=-4. Since m+=+77%2F9+-+1%2An%2F9, m=9.

Answer: system%28+m=9%2C+n=-4+%29.



I hope the above steps and explanation were helpful.

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Also, good luck in your studies and contact me at john@e-liteworks.com for your future math needs.

Respectfully,
Dr J

Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!
solve by subsititution method 9m+n=77 m-3n=21

9m + n = 77 ------ (i)
m - 3n = 21 ------(ii)

m = 21 + 3n ----- Solving for m in eq (ii)

9(21 + 3n) + n = 77 ------ Substituting 21 + 3n for m in eq (i)

189 + 27n + n = 77

28n = - 112

n = -112%2F28 = highlight_green%28-4%29

m - 3(-4) = 21 ----- Substituting - 4 for n in eq (ii)

m + 12 = 21

m = 21 - 12 = highlight_green%289%29