Question 1121536
Between 15 and 18 wins is a z of (15-17.3)/2.2 and a z of (18-17.3)/2.2
this is a z from -1.045  to 0.32. That probability is 0.4775

For 21 or more than 21 wins would be a z of  (21-17.3/2.2 or 1.68
probability z is greater than that is 0.0237

One cannot use the Gaussian distribution to determine exactly 21 wins, since it is continuous and each point is infinitesimally small.  One would need a probability of winning each game, if it were independent (not likely) and use a binomial distribution.