1. EXAMPLE 3 Writing and Solving an Inequality Owning a Business You use the Internet to sell mouse pads. You pay a wholesaler $6 for each mouse pad. You then sell the mouse pads for $10 each. You pay $21 per month for Web page hosting. How many mouse pads should you sell each month to earn a profit? SOLUTION To earn a profit, your revenue must be greater than your expenses

2. EXAMPLE 3 Writing and Solving an Inequality 10x > 6x + 21 Write an inequality. 4x > 21 Subtract 6x from each side. x > 5.25 Divide each side by 4. ANSWER You cannot sell part of a mouse pad. So, you should sell at least 6 mouse pads per month to earn a profit.

3. GUIDED PRACTICE for Example 3 Nutrition 4. A membership at a nutrition store costs $20 per year. You can buy vitamins for $18 a bottle without a membership, and $15 a bottle with a membership. How many bottles of vitamins do you need to buy each year to make a membership worthwhile? ANSWER 7 or more bottles.