Answer:
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the answer is JKN = 57
Explanation:
JKN is JKL + LKN
we know that LKM = 42, and LKN is half of that because KN bisects LKM (splits into 2 equal parts)
so, LKN is half of 42
LKN = 21
to find JKL, subtract 42 from 78
JKL = 36
36 + 21 = 57