We can draw the situation as:
So, if L is the midpoint of JM, JL is equal to LM and JM is equal to 2 times JL
JL = LM
JL + LM = JM
JL + JL = JM
2JL = JM
We can calculate JM using JL as:
2JL = JM
2*15 = JM
30 = JM
Then, if K is the midpoint of JL, JK is equal to KL and JL is 2 times JK
JL = 2JK
Replacing JL by 15, we get:
15 = 2JK
15/2 = JK
7.5 = JK
Finally, KM can be calculated as:
KM = JM - JK
KM = 30 - 7.5
KM = 22.5
Answer: 22.5
