Jis the midpoint of hk. what is hj, jk, and hk

Hj and jk are the same length line segments ( because the midpoint divides a line into two equal parts)
So hj = jk.

hk is the line segment which has the mid point j. It is the double of hj or jk. It can be the sum of hj and jk. 
hj + jk = hk 
      or
2 * hj = hk
      or 
2 * jk = hk

First subtract 10 from both side
y^2+6y-16=0
(y+8)(y-2)=0
-8 and 2