How many variable terms are in the expression 3x3y + 5x2 + y + 9?

Which of the following is correct interpretation of the expression -4+13

If the cost to mail a package is an initial $5 and $0.28 for every pound the total cost to mail a package was $11.27, how much did the package weigh?

Barbara deposited $300 in the bank. if the bank pays her simple interest at the rate of 4 percent per year, how much money will she have in her account at the end of 9 months?