The problem is to solve the system of two equations: $b = -a$ $-12 = -6a$ for the variables $a$ and $b$.

1. Problem Description

The problem is to solve the system of two equations:

$b = -a$

$-12 = -6a$

for the variables $a$ and $b$.

2. Solution Steps

We have two equations:

(1) $b = -a$

(2) $-12 = -6a$

From equation (2), we can solve for $a$:

$-12 = -6a$

Divide both sides by $-6$:

$\frac{-12}{-6} = \frac{-6a}{-6}$

$2 = a$

$a = 2$

Now that we have $a = 2$, we can substitute this value into equation (1) to find $b$:

$b = -a$

$b = -2$

3. Final Answer

$a = 2$

$b = -2$