20
1) Segment Addition Postulate. Let's draw this Line Segment to better understand this
The length of KM is going to be the sum of KL and LM.
2) Since L belongs to the Line Segment KM, and those Line segments are measured as 11 and 9 we can write:
KM = KL +LM
KM =11+9
KM =20
Therefore, KM measures 20.
