Chapter 2 - Solving Equations - 2-5 Literal Equations and Formulas - Practice and Problem-Solving Exercises - Page 114: 56

$a=-4$

$4+12a=-2(6-4a) \\\\ 4+12a=-12+8a \\\\ 4+4a=-12 \\\\ 4a=-16 \\\\ a=-4$ We first use the distributive property on the right side of the equation to simplify. We then subtract by 8a on both sides. Next, we subtract by 4 on both sides. Finally, we divide by 4 to get that $a=-4$.