Draw the segment JL, place k at the midpoint. This will make it easier to follow my explanation.
If K is the midpoint of JL;
JK = KL, so;
5x = 3x + 2
subtract 3x from both sides:
2x = 2
divide both sides by 2:
x = 2/2 = 1
JK = 5x = 5
KL = 3x + 2 = 3 + 2 = 5
JL = JK + KL = 5 + 5 = 10