Let's begin by listing out the information given to us:
Guitar price (P) = $670, discount (d) = 10%, sales tax (s) = 8%
It is bought on a one year installment plan; 15% of price upfront + taxes
a.
The discount is 10%
The discounted price is given by the product of the guitar price by dicount =
discount = $670 & 10% = 670 * 0.01 = $67
b.
The sales price is given by the difference between the guitar price minus the discount