How to solve 7m + 2n = 21 and 10m + 4n = -10 using substitution. step by step and you!

7m+2n=21
-7m      -7m

2n=21-7m 
2        2

n=21-7m
      2

10m+4(21-7m/2)= -10
-10m                   -10m

4(21-7m/2)= -10-10m

(84-28m/2)= -10-10m
    x2                x2

84-28m    = -20-20m
+20+28m   +20+28m

104 = 8m
8         8

m=13

10(13) + 4n = -10
-130              -130

4n = -140
4         4

n= -35

If anything is unclear please feel free to ask.

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