42=12a-42

Solution for 42=12a-42 equation:

Simplifying
42 = 12a + -42

Reorder the terms:
42 = -42 + 12a

Solving
42 = -42 + 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 = -42 + 12a + -12a

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

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

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

Combine like terms: -42 + -42 = -84
-12a = -84

Divide each side by '-12'.
a = 7

Simplifying
a = 7