Răspuns:
DE || BC => ∆ADE ~ ∆ABC
AD/AB = AE/AC = DE/BC
10/24 (2 = AE/48 = DE/BC
5/12 = AE/48
AE × 12 = 48 × 5
AE × 12 = 240
AE = 20
DE = AD + AE
DE = 10 + 20
DE = 30
BC = AB + AC
BC = 24 + 48
BC = 72
/ \ A
/ \
D /------\ E
/ \
B /_______\ C
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