Answer:
12
Explanation:
I find it convenient to use the following relation:
JL -KL +5 = JM
(x +7) -(2x -4) +5 = 3x . . . . . substituting values shown
16 -x = 3x . . . . . . . . . . . . . . . collect terms
16 = 4x . . . . . add x
4 = x . . . . . . . divide by 4
JM = 3x = 3·4 . . . . . . find the length of JM
JM = 12