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Question 5 spring semester final exam math evaluate

There are 15 plates and each plate is either 7 or 12 inches diameter. which systems of equations do you use to find the number of 7 inch plates, x and 12 inch plates, y

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?