If 3m+4n=47, and m+n=15-2m, what is m?
3m + 4n = 47 (1)
m + n = 15-2m → 3m + n = 15 → n = 15 - 3m (2)
Sub (2) into (1)
3m + 4 (15 - 3m) = 47
3m + 60 - 12m = 47
-9m = 47 - 60
-9m = -13
m = 13 / 9