Tentukan panjang DB.Jawablah dg benar

ED/BC = AD/AB
8/12 = 10/(10 + DB)
2/3 = 10/(10 + DB)
2(10 + DB) = 30
10 + DB = 15
DB = 5 cm

(10 + DB) / 12 = 10 / 8
(10 + DB) / 12 = 5 / 4
4(10 + DB) = 5 x 12
4(10 + DB) = 60
10 + DB = 60 / 4
10 + DB = 15
DB = 15 - 10
DB = 5 cm