Question

A weight suspended from a spring is seen to bob up and down over a total distance of 20 centimeters twice each second.

8. What is the frequency?

9. What is the period?

10. What is the amplitude?

Answer 1

"Twice each second" means "2 per second".  Frequency = 2 Hz.

Period = time for one bounce = 1 second

Amplitude = distance between "not stretched" and "greatest stretch".

Amplitude =  10 centimeters