Can you guys help meh pls

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 number 321,000,000 in scientific notation? also what is the number? ?

Which of the following quartic functions has x = –1 and x = –2 as its only two real zeroes?