42=3(-4a)+6

Solution for 42=3(-4a)+6 equation:

Simplifying
42 = 3(-4a) + 6

Remove parenthesis around (-4a)
42 = 3 * -4a + 6

Multiply 3 * -4
42 = -12a + 6

Reorder the terms:
42 = 6 + -12a

Solving
42 = 6 + -12a

Solving for variable 'a'.

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

Add '12a' to each side of the equation.
42 + 12a = 6 + -12a + 12a

Combine like terms: -12a + 12a = 0
42 + 12a = 6 + 0
42 + 12a = 6

Add '-42' to each side of the equation.
42 + -42 + 12a = 6 + -42

Combine like terms: 42 + -42 = 0
0 + 12a = 6 + -42
12a = 6 + -42

Combine like terms: 6 + -42 = -36
12a = -36

Divide each side by '12'.
a = -3

Simplifying
a = -3