Question

Breyanna is buying a new dress .The dress is on sale for 20% off.Breyanna will also have to pay 10% sales tax on the discounted price of the dress.The expression below shows the total amount, including the tax, that Bianca will pay for a dress which originally cost x dollars.
(x-0.20x)+0.10(x-0.20x)


What percent of the dress original price will Breyanna pay?

Answer 1

Hi,
Let x be 100 dollars(since per cent means out of 100)(also SP)
SP without sales tax= 100 - d%/100 * SP
= 100-20/100 * 100
=80/100 * 100
= 0.8 * 100
= 80 dollars=SP without tax
tot. SP(SP with tax)= 100 + tax%/100 * SP
=100 + 10 /100 * 80
= 110/100 * 80
= 11/10 * 80
=1.1* 80
=88%
Breyanna will have to pay 88% of the dress original price. 
Hope this helps you.