Help! I'm being timed!

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

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?

For a function f(x), a) if f(7) = 22 then f^-1(22) = b) f^-1(f(c)) =