Answer: MN = 7
Explanation:
LM + MN = LN by the segment addition postulate. This says we can break up a segment into smaller pieces, and have those pieces add back up to the original length.
Plug LM = 5 and LN = 12 into the equation and isolate MN to get
LM + MN = LN
5 + MN = 12
MN = 12-5
MN = 7
See the diagram below.
