If K is the midpoint, we know they must be of equal lengths. So we can set them equal to each other and solve for x.
8x - 8 = 7x - 6 ---> subtract 7x from both sides
x - 8 = -6 ---> add 8 to both sides
x = 2
Then to find JL, put the 2 into either equation and double it.
8(2) - 8 = 8
8*2 = 16
The length of JL = 16