Jamie purchased a DVD that was on sale for 15% off. The sales tax in her county is 5%. Let y represent the original price of the DVD. Write an expression that can be used to determine the final cost of the DVD.
Since the DVD has 15% off its original price, then that means:
100% - 15% =85% which is the sale price you pay,
Since the original price was "y", then:
85%y + 5% sales tax =The final sale price, or
0.85y + 0.05(0.85y) =The final sale price.
+51 
