m+(3+m)(-2)=78

Solution for m+(3+m)(-2)=78 equation:

Simplifying
m + (3 + m)(-2) = 78

Reorder the terms for easier multiplication:
m + -2(3 + m) = 78
m + (3 * -2 + m * -2) = 78
m + (-6 + -2m) = 78

Reorder the terms:
-6 + m + -2m = 78

Combine like terms: m + -2m = -1m
-6 + -1m = 78

Solving
-6 + -1m = 78

Solving for variable 'm'.

Move all terms containing m to the left, all other terms to the right.

Add '6' to each side of the equation.
-6 + 6 + -1m = 78 + 6

Combine like terms: -6 + 6 = 0
0 + -1m = 78 + 6
-1m = 78 + 6

Combine like terms: 78 + 6 = 84
-1m = 84

Divide each side by '-1'.
m = -84

Simplifying
m = -84