His mean score for the first 4 games will be 18 points.
Explanation
In the first 3 games, the mean of the scores is 15 points . Mean is the simple average of some numbers.
So, the total score in first 3 games = points
Now, in the 4th game, he scored 27 points. So, the total score in the first 4 games = points
Thus, the average of scores in first 4 games = points
So, his mean score for the first 4 games will be 18 points.
