Answer
$25$ oscillations
Work Step by Step
We know that the formula to be used here is: $T=2\pi \sqrt{\frac{m}{k}}$
Substituting the values in the formula above, T is:
$T=2\pi \sqrt{\frac{0.80kg}{200N/m}}=0.397s$
Oscillations completed in ten seconds is found through the formula:
$\frac{10 s}{0.397s}=25$ oscillations
