Solve the matrix equation for x. 3x =13 21] 11. [21 2x]-18 $1=[7 3] In Exercises, 12-15, use the following information. Book Prices: The matrices below show the number of books sold and the average price (in dollars) for the years 2002, 2003, and 2004. 2002 (A) 2003 (B) 2004 (C) Sold Price sold Price Sold Price Book A [125,000 52.007 110,000 55.507 90,000 47.501 Book B 85,000 83.50 95,000 85.50 100,000 89.00 190,000 45.601 210,000 56.25. 225,000 75.25] Book C 12. You purchased book A in 2002, book C in 2003, and book B in 2004. How much did you spend on these three books? 13. How many more (or less) volumes of book B were sold in 2004 than in 2002? 14. How much more (or less) is the price of book A in 2004 than in 2002? 15. In 2005, would you expect book C sales to more or less than 100,000