Answer
$(22, -6)$
Work Step by Step
By using the midpoint formula, we have
$$(x, y)=\left(\frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}\right)$$
$$(8, 2)=\left(\frac{-6 + x_2}{2}, \frac{10 + y_2}{2}\right)$$
Thus,
$$\dfrac{-6 + x_2}{2}=8 \\
-6 + x_2 =16\\
x_2 = 16+6\\
x_2 = 22$$
and
$$\frac{10 + y_2}{2}=2\\
10 + y_2 =4\\
y_2=4-10\\
y_2 = -6$$
Therefore, the coordinates of $B$ are $(22, -6)$.