Explanation: By multiplying 0.10 (4,000) to find the interest for one year, you get 400. Because she is using this loan for 4 years you multiply that one year interest by 4. 400 times 4 is 1600. Then, you add that 1600 (which is the total interest for 4 years) to the loan, to get an answer of 5,600.
The books are $5, and the magazines are $10. I’m not sure which way you want it explained but since magazines are twice the price of books, you can solve the equation 3b + 2b = 25. This gives you b=5 which you just multiply by 2 giving you the price of a magazine.
