Answer
$(22,-6)$
Work Step by Step
Step 1. Assume the coordinates of B is $B(x,y)$, the midpoint formula for AB gives $(\frac{x-6}{2},\frac{y+10}{2})$
Step 2. Let $\frac{x-6}{2}=8$, we have $x=22$
Step 3. Let $\frac{y+10}{2}=2$, we have $y=-6$
Step 4. Thus we have $B(22,-6)$