tolong kak...............

CE = 3 m
DE = 4 m
BC = 12 m
AB = ....??

CE/BC = DE/AB
3/12 = 4/AB
3 × AB = 4 × 12
3AB = 48
AB = 48/3
AB = 16

Jadi lebar sungai AB adalah 16 m (a)

Kesebangunan

ΔABC  sebangun Δ DEC
<B = <E ( 90°)
<C = <C  (bertolak belakang)
<A = < D

lebar sungai = AB
AB/BC = DE/EC
AB/12 = 4/3
AB = 4/3 x 12
AB = 16
Lebar sungai = 16 m