Only answer if you actually know the answer, and is able to explain everything cait purchased a $20 item at a store. she uses a coupon to receive a 15% discount, and she pays a 6% sales tax on item. she calculates the total cost, in dollars, of the item using the expression: (1.15)(1.06)(20) a. describe the error in the expression cait used for her calculations. b. show or explain how you would calculate the total cost of cait's purchase.

A. Describe the error in the expression Cait used for her calculations.
 For this case we have:
 She uses a coupon to receive a 15% discount:
 (100-15) * (1/100) = 0.85
 she pays to 6% sales tax on item:
 (100 + 6) * (1/100) = 1.06
 Therefore, the error is given by:
 (1.15) (1.06) (20)
 the term 1.15

 B. Show or explain how you would calculate the total cost of Cait's purchase.

 The total cost for this case is given by the following expression: 
 (0.85) (1.06) (20)
 Calculating we have:
 $ 18.02