P(8 or 12) = 1/6
P(not 8 or 12 = 5/6
Let the expected points fro one roll be X.

The answer is -(1/6) points.
P(blue) is 23/82 the sum is 82 and there is 23 blue balls
20% off means you pay 80% of the price so you multiply by 0.8, and 7% tax means you multiply by 1.07
Resulting cost = 18.99*0.8*1.07 = 16.26
Hope this helps let me know if im wrong!