12=-3a-a

Solution for 12=-3a-a equation:

Simplifying
12 = -3a + -1a

Combine like terms: -3a + -1a = -4a
12 = -4a

Solving
12 = -4a

Solving for variable 'a'.

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

Add '4a' to each side of the equation.
12 + 4a = -4a + 4a

Combine like terms: -4a + 4a = 0
12 + 4a = 0

Add '-12' to each side of the equation.
12 + -12 + 4a = 0 + -12

Combine like terms: 12 + -12 = 0
0 + 4a = 0 + -12
4a = 0 + -12

Combine like terms: 0 + -12 = -12
4a = -12

Divide each side by '4'.
a = -3

Simplifying
a = -3