tolong dijawab bsk d kmpl pke jalanny

a.
DE / DC = AB / AC
DE / 4 = 12 / 6
DE / 4= 2
DE = 2 x 4
DE = 8 cm

b.
CB / AC = CE / DC
(5 + EB) / 6 = 5 / 4
4(5 + EB) = 6 x 5
20 + 4EB = 30
4EB = 30 - 20
4EB = 10
EB = 10 / 4
EB = 2,5 cm