With intersecting lines, the angles opposite the intersection (across the "X") are called vertical angles, and they are identical. Therefore JNK = MNL and KNL = JNM.
So set KNL = JNM:
3(x+14) = 5x+2
3x+42 = 5x+2
3x+42 -42 = 5x+2 -42
3x = 5x -40
3x -5x = 5x-5x -40
-2x = -40
-2x/-2 = -40/-2
x = 20
Now plug that into x for KNL:
KNL = 3(x+14) = 3(20+14) = 3(34) = 102°