1)
You could do this problem the rigorous way and look up the probability of the high and low z-scores,
but because each of the bounds are integer multiples of the standard deviation, -2, and 2, about the mean,
I suspect they want you to know that
\(P[(\mu -\sigma,\mu+\sigma)]\approx 0.68\\ P[(\mu -2\sigma,\mu+2\sigma)] \approx 0.95\\ P[(\mu-3\sigma, \mu+3\sigma)] \approx 0.997\\ \text{etc.}\)
So we are looking at 95% of the total population of 300 gamers.
This is 285 people.