The average points per game is computed as follows:
(10 + 12 + 10 + 8 + 14 + 15 + x)/7
where x are the points in the last game. We want the average to be 12, then:
(10 + 12 + 10 + 8 + 14 + 15 + x)/7 = 12
Solving for x:
10 + 12 + 10 + 8 + 14 + 15 + x = 12*7
69 + x = 84
x = 84 - 69
x = 15