help me with my math quickly!!!!

Answer:
The best way to find out cost of purchase (add each dollar amount for each shopper) Then take that number and multiple it by the tax rate. The product of that will give you sales tax. Add the cost of purchase and the sales tax, to get the total amount paid.
Step-by-step explanation:
For example: Serena
29.00 + 18.79 = 47.79 Cost of Purchase
47.79 x .05 = 2.39 Sales Tax
47.79 + 2.39 = 50.18 Total Amount Paid