Jawabanmu

2014-08-19T19:40:42+07:00
Jarak (x) =18 m
cepat rambat (v) = 12 m/s
n = ....?
x = v.t
18 = 12.t
12t = 18
t = 3/2
f = n/t
n = f.t
   = 4.3/2
   = 6
Jadi banyaknya gelombang = 6 gelombang