On the coordinate grid of a map. jeff's house is located at (9,5). hannah's house is at (-5,-5). kenya's house is located at the midpoint between jeff and hannah's houses. what is the distance from hannah's house to kenya's house?

The midpoint formula is 
So just plug in the corresponding coordinates in the correct place to get the midpoint.
x_1=-5 ; x_2=9 ;  y_1=-5 ; y_2=5
((-5 + 9)/2 , (-5 + 5)/2)
(4/2 , 0/2)
(2,0) is where Kenya's house is(which is the midpoint). 

The distance formula is a bit more complicated than that. The distance formula is D=
In this case now, your looking for the distance from Hannah's house to Kenya's house.
D=
=
= ≈8.6023