There is not sufficient information to answer the question. To solve for two unknown variables (d and m) you need two independent equations.
9m + 9m + 3m + 3m = 24m
m + m + m
If: 3m = 78 Then: m = 26
3m = 14 m = 14/3
-3m
3m-5 = 7-21 3m = 7-21+5 3m = -9 m = -3
-3m + 8 = 2 -3m = 2 - 8 -3m = -6 m = -6/-3 m = 2
3m + 15 = 45 3m = 30 m = 10
-3m = 5m+8 -3m-5m = 8 -8m = 8 m = -1
If: m = 20 Then: 3m+18 = 78
If: 7+3m = -29 then the value of m is -12
3m + 11n = 3