Number of DVDs * Cost of DVDs = Total Cost of DVDs
4 * 9.99 = 39.96
10% of 39.96 = 3.996
3.996 * 2 = 20%
7.992 = 20%
Total Cost of DVDS - Discount = Cost
39.96 - 7.992 = 31.968
Cost + Sales Tax = Total Cost
31.968 + 7.75 = $39.718
The answer is $39.718 or $39.72