By placing point K on the line segment JL, you now have two connected line segments JK and KL, and the total length of JL is equal to the sum of the lengths of JK and KL. So we have
4x + 9 = (5x + 2) + (2x - 2)
Solve for x :
4x + 9 = 7x
9 = 3x
x = 3
Then the total length of JL is
4x + 9 = 4•3 + 9 = 12 + 9 = 21