cost of the CD ($) + sales tax amount ($) = total price of the purchase ($)

 understand that the sales tax amount depends on the price of the item(s) you're purchasing, in this case, the sales tax amount is 7.5% of $12.00. To find this amount, you first have to convert the sales tax from percent form to decimal form:

                                               7.5% / 100% = 0.075

and so, ($12.00) + ($12.00 * 0.075) = $12.00 + $0.90 = $12.90

Total Price = Cost of CD + Sales Tax 

Cost of CD: $12

Sales Tax: 7.5% of $12

To find sales tax amount:

1. change the percentage to a decimal by dividing the percentage by 100:

7.5% / 100% = 0.075

2. Multiply the cost of the CD by the decimal amount:

0.075 x $12.00 = $0.90 - this is the sales tax amount

To find total sales price: Add cost of CD to sales tax amount

$12 + $0.90 = $12.90