A small mass attached to a spring oscillates with simple harmonic motion with amplitude of 70 mm, taking 13 seconds to make 40 complete oscillation. Calculate its angular frequency?

Answer 1

You don't need the amplitude to compute the frequency. The fact that it is a mass and spring is also not needed.

The frequency is 40/13 = 3.08 oscillations per second or "Hz".
Multiply that by 2 pi and you get 19.3 radians/s for the angular frequency.