You know IK (the whole line segment) is equal to 16, so make the line segments within IK (IJ and JK) add up to 16 in an equation, then solve for x and plug it into IJ to find IJ.
IJ + JK = IK
4x + (2x - 2) = 16
Combine like terms.
6x - 2 = 16
Add 2 to both sides.
6x = 18
Divide both sides by 6.
x = 3
Plug 3 for x into IJ (4x).
4(3) = 12
IJ = 12
