pake cara pls tolong bantuannya no 10

Dik :CF : FB = 1 : 3
        AB = 18 cm
        DC = 6 cm
Dit : EF = ?
Jawab :
Pake rumus air mancur ya

EF = (CF . AB + FB . DC)/CF + FB

EF = (1 . 18 + 3 . 6)/1+3

EF = (18+18)/4

EF = 36/4

      = 9 cm (B)

Maaf klo  salah ya