What's the answer to this problem

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

Find the zero function by factoring (try to show work) h(x)=-x^2-6x-9

Ineed with number 6 , explain how to get 1978