tolong...................................

kesebangunan

ΔDEC  sebangun  ABC
AB = 5
BC = 12
BE = 4
CE + EB +  = BC
CE + 4 = 12
CE  = 12-4 = 8

CE/DE  = CB/AB
8/DE = 12 / 5
DE = 5 (8) / 12
DE = 40/12
DE = 10/3 cm