Graph the function y=1/2sin(x-pi/4)

Ifurniture stores having a weekend sale and is offering 20% discount on patio chairs and table the sales tax on furniture is 6.25 using function composition how can you represent the total amount a that you would need to pay for this furniture that cost x dollars

If jaime wants to find 60% of 320, which table should he use?

How to do this , and can some one explain