Again, I already know this answer... It's 12 but I do not know how to come up with this answer. Plz show me step by step how to come up with the correct answer. My test is tomorrow. Thank you in advance!!

A basketball player averaged 20 points a game over the course of six games. His scores in five of those games were 23, 18, 16, 24, and 27. How many points did he score in the sixth game?

20 * 6 = 120

23 + 18 + 16 + 24 + 27 + x = 120