Given,
The mass attached to the spring, m=0.520 kg
The stretching of the spring, x=18.7 cm=0.187 m
The restoring force of spring is given by,

Where k is the spring constant of the spring.
The force F is equal to the weight of the mass attached.
Thus,

Where g is the acceleration due to gravity.
On substituting the known values,

The frequency of the spring is given by,
![f=(1)/(T)=(1)/(2\pi)\sqrt[]{(k)/(m)}](https://img.qammunity.org/2023/formulas/physics/college/yhsm3sze7au1nkgdmrtdjn7x89xgal0rlf.png)
where T is the period of oscillation of spring.
On substituting the known values,
![\begin{gathered} f=(1)/(2\pi)\sqrt[]{(27.3)/(0.520)} \\ =1.15\text{ Hz} \end{gathered}](https://img.qammunity.org/2023/formulas/physics/college/s5h3xy1q7bu1di244q39qj3j0tjrfuqzwl.png)
Thus the frequency of oscillation of the spring is 1.15 Hz.