Please help guys please

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

What is the range of the relation in the table below? x y –2 0 –1 2 0 4 1 2 2 0

How do you determine if an ordered pair is a solution to a given equation?