Find the midpoint of side ef. figure efgh is shown. e is at negative 2, 3. f is at 1, 6. g is at 4, 3. h is at 1, 0.

Because E's order pair is (-2,3) and F's order pair is (1,6) all you have to do is find the middle you can do this multiple ways but the easiest is crossing out the middle and see what is leave 
so 
for the x point 
-2,-1,0,1 
the middle here is -0.5
while for the y point 
3, 4, 5, 6 
the middle here is 4.5 
so your order pair is (-0.5,4.5)

if you wanted to do the algebraic way all you have to do is use the middle point formula which is 
(x1+ x2)/2 ,(y1+y2)/2
which is for the x
-2+1/2
-1/2
-0.5
while for the y 
3+6/2
9/2
4.5