Chapter 2 - Solving Equations - 2-2 Solving Two-Step Equations - Practice and Problem-Solving Exercises - Page 91: 29

$a=-2$

We need to get the a alone. In order to cancel out division, we use multiplication, so we multiply both sides by 2 to get that a+10=8. We now cancel out the addition by subtracting 10 on both sides, giving us a final answer of $a=-2$. We plug -2 in for a and confirm that our answer is, indeed, correct.