1. EXAMPLE 1 Solving a Real-World Problem Music Club You pay $9.95 to join an Internet music club. You pay $.99 for each song that you download. Your cost for joining and downloading some songs is $17.87. How many songs did you download?

2. EXAMPLE 1 Solving a Real-World Problem The model below represents a way of finding how many songs you downloaded. You can use x to represent the number of songs.

3. EXAMPLE 1 Solving a Real-World Problem SOLUTION –9.95 0.99x7.92 = 0.99x 7.92 0.99 x = 8 Write an algebraic model. Subtract 9.95 from each side to undo addition. Simplify. Divide each side by 0.99 to undo multiplication. Simplify. x is by itself. ANSWERYou downloaded 8 songs. = 17.87 9.95 + 0.99x

4. for Example 1 GUIDED PRACTICE 1. Show how to check the solution in Example 1. 17.87= 17.87 9.95 ? = 17.87+ 7.92 + 0.99 9.95 ? = 17.87 8

5. for Example 1 GUIDED PRACTICE SOLUTION Cost to join + Cost per song Number of songs = Total cost Write an algebraic model. –9.95 Subtract 9.95 from each side to undo addition. 0.99x 16.83 = Simplify. 9.95 + 0.99x = 26.78 2. What If? Suppose the cost to join and download some songs is $26.78. How does this change the equation in Example 1 ? Find the number of songs.

6. for Example 1 GUIDED PRACTICE Divide each side by 0.99 to undo multiplication. 0.99x 16.83 0.99 = x = 17 ANSWERYou downloaded 17 songs.

7. for Example 1 GUIDED PRACTICE 3. Film You pay $35 in dues to a photo club and $10 per roll you have developed. If you spend $225 during the year, how many rolls of film do you have developed? Use 10x + 35 = 225 and solve for x. ANSWERYou developed 19 rolls of films.