(-3a-6)=42-7a

Solution for (-3a-6)=42-7a equation:

Simplifying
(-3a + -6) = 42 + -7a

Reorder the terms:
(-6 + -3a) = 42 + -7a

Remove parenthesis around (-6 + -3a)
-6 + -3a = 42 + -7a

Solving
-6 + -3a = 42 + -7a

Solving for variable 'a'.

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

Add '7a' to each side of the equation.
-6 + -3a + 7a = 42 + -7a + 7a

Combine like terms: -3a + 7a = 4a
-6 + 4a = 42 + -7a + 7a

Combine like terms: -7a + 7a = 0
-6 + 4a = 42 + 0
-6 + 4a = 42

Add '6' to each side of the equation.
-6 + 6 + 4a = 42 + 6

Combine like terms: -6 + 6 = 0
0 + 4a = 42 + 6
4a = 42 + 6

Combine like terms: 42 + 6 = 48
4a = 48

Divide each side by '4'.
a = 12

Simplifying
a = 12