JK = 18m
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Step-by-step explanation:
ΔJLK = ΔNLM ( vertically opposite Δ)
ΔJKL = ΔNML ( each 90° )
so,
triangle JKL = triangle NML (by AA similarity)
JK / KL = NM / ML
JK / 21m = 42m / 49m
JK = 42 × 21 ÷ 49
JK = 18m
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