Answer:
64 units
Explanation:
Segment addition holds, so we can write ...
LM + MN = LN
(10x +8) +(5x-4) = (12x +16)
15x + 4 = 12x + 16 . . . . . . . . collect terms
3x -12 = 0 . . . . . . . . . . . . . . subtract 12x+16
x-4 = 0 . . . . . . . . . . . . . . . . . divide by 3
x = 4 . . . . . . . add 4
LN = 12x +16 = 12·4 +16 = 48 +16 . . . . . substitute into the expression for LN
LN = 64 . . . . units