tentukan lebar sungai,pls tolong jawab poinnya tinggi!!!

CB = lebar sungai

CB/(CB + CA) = BD/AE
CB/(CB + 6) = 2/3
3CB = 2CB + 12
3CB - 2CB = 12
CB = 12 m

H = (H+6) x (BD/AE)
H = (H+6) x (2/3)
H = 2H/3 + 4
H - 2/3H = 4
1/3H = 4
H = 4 x 3/1
H = 12