A basketball team scored x points per game in its first n games of the

This is my thought process.
First, lets organize the information at hand.
X = the average points per first n games
N = the first # of games played
Y = the average points per game after the first N games
3 = games after N, so this is Y
Objective, What is the average points per game for x + y games?

Ok, so we need to get an average of points. What do we do to get an average number of something? Its total points/number of games played (which we already have! n + 3). So we just need to figure out the numerator.
We can get the total points by multiplying the number of games n and the average points per first n games, which is x, and all games after the N games, i.e. 3 games, multiply that with the average points per game after the first N games, which is y.

Looking like (nx + 3y)/ (n + 3)

The answer is D