Answer:
The midpoint of CD is (3, -3.5). The midpoint of EF is (-1.85, -5.4).
Explanation:
The example in the textbook explains it pretty clearly, and assuming you guys can use calculators (or not, either way) this should hopefully make sense.
1) Write out the 2 coordinate pairs.
2) Group the x-coordinates together, and group the y-coordinates together.
3) Add the 2 x-coordinates together, and divide the answer by 2.
4) Add the 2 y-coordinates together, and divide the answer by 2.
5) The resulting coordinate pair (x,y) is your midpoint.
I attached a picture showing how to do 1a., so you should be able to figure out 1b.