Both A And B Are what I’m stuck on.can someone please give me the answers

In what form is the following linear equation written y=9x+2

Steve wants to develop a way to find the total cost of any item including sales tax. the sales tax in his city is 6%. his friend jenna writes the expression x + 6x where x is the cost of the item. explain whether her expression is correct based on the situation.

What is the point of inflection for the function f(x)=2cos4x on the interval (0, pi/2)