Chapter 1 - Review Exercises - Page 109: 58

$2$

Start at $-6$. Adding a positive number means you move to the right. Thus, adding 8 means you move 8 units to the right. From $-6$, if you move 8 units to the right, you will end up at $2$. Thus, $-6+8=2$ (refer to the image below for the number line addition)