4. The masses of a sheet of writing paper and an envelope are 3 g and 5 g respectively. It costs 60 cents to send a letter with mass not exceeding 20 g . Michael has 60 cents worth of stamps. If \( x \) is the number of sheets of writing paper, form an inequality in \( x \) and find the maximum number of sheets of writing paper that he can use.

To determine the maximum number of sheets of writing paper Michael can include in his letter without exceeding the mass limit of 20 grams, follow these steps: 1. **Identify the Mass Components:** - **Envelope:** 5 grams - **Each sheet of writing paper:** 3 grams - **Total mass limit:** 20 grams 2. **Set Up the Inequality:** The total mass of the letter consists of the mass of the envelope plus the mass of the writing papers. Therefore, the inequality can be expressed as: \[ \text{Mass of Envelope} + (\text{Number of Sheets} \times \text{Mass per Sheet}) \leq \text{Total Mass Limit} \] Substituting the given values: \[ 5\, \text{g} + 3x \leq 20\, \text{g} \] Where: - \( x \) = number of sheets of writing paper 3. **Solve the Inequality for \( x \):** \[ 5 + 3x \leq 20 \] Subtract 5 from both sides: \[ 3x \leq 15 \] Divide both sides by 3: \[ x \leq 5 \] 4. **Conclusion:** Michael can include a **maximum of 5 sheets** of writing paper in his letter without exceeding the 20-gram mass limit. **Final Answer:** The inequality is 5 + 3 x ≤ 20. The maximum number of sheets Michael can use is five.