What is the midpoint of the segment connecting (-3, 7) and (9, -1)?

The midpoint is the average of the coordinates: $\left(\frac{-3+9}{2},\ \frac{7+(-1)}{2}\right)=\left(\frac{6}{2},\ \frac{6}{2}\right)=(3,3)$, choice A. Choice B, $(6,6)$, adds the coordinates but forgets to divide by $2$. Choice C, $(3,4)$, makes a sign error on the $y$-values, computing $\frac{7+1}{2}=4$. Choice D, $(-6,8)$, subtracts the coordinates and does not divide. The midpoint should lie between the endpoints, and $3$ is between $-3$ and $9$, and $3$ is between $-1$ and $7$, which supports choice A.