I need help pls

How do you answer this question? (step by step)

If there are 12 moths and some have 31 days and others have 30 days how many have 28 days?

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.