Can someone please explain this?

Which expression is equivalent to (9x - 3 1/ + 1 3/8)

Kayla made observations about the sellin price of a new brand of coffee that sold in the three different sized bags she recorded those observations in the following table 6 is $2.10 8 is $2.80 and 16 is to $5.60 use the relationship to predict the cost of a 20oz bag of coffee.

What is the inverse of the function f(x) = 2x + 1?