Answer :
1). Frequency = (1/period) = 1/(20sec) = (1/20) per sec .
2). Frequency= (3 waves) / (4 sec) = (3/4) (per sec)
Period = (1/freq) = 1/(3/4 per sec) = (4/3) sec
3). Speed= (freq) x (wavelength) (2 per sec) x (5 m) = (2 x 5) ( m per sec)
Speed doesn't depend on amplitude.