Tentukan nilai x pada gambar berikut !

CD / CA = CE / CB
9 / 3+9 = 12 / 12+x
9 / 12 = 12 / 12+x
3 / 4 = 12 / 12+x
3 (12 + x) = 12 (4)
36 + 3x = 48
3x = 48 - 36
3x = 12
x = 12/3
x = 4