7m+n=34 ,m-8n=13

Question

solve by the substitution method

7m+n=34

m-8n=13

Answer 1

Problem: 7m+n=34 ,m-8n=13
solve by the substitution method
7m+n=34
m-8n=13

7m + n = 34
m - 8n = 13

m - 8n = 13
m - 8n + 8n = 13 + 8n
m = 13 + 8n

7m + n = 34
7(13 + 8n) + n = 34
7(13 + 8n) + n = 34
91 + 56n + n = 34
91 + 57n = 34
91 + 57n - 91 = 34 - 91
57n = -57
57n/57 = -57/57
n = -1

m - 8n = 13
m - 8(-1) = 13
m + 8 = 13
m + 8 - 8 = 13 - 8
m  = 5

Always check.

7m + n = 34
7(5) + (-1) = 34
35 - 1 = 34
34 = 34

m - 8n = 13
5 - 8(-1) = 13
5 + 8 = 13
13 = 13

Answer: m = 5, n = -1