1. **State the problem:** Find the mean of the data set represented by the stem-and-leaf plot: Stem | Leaf 0 | 8 1 | 2 7 8 9 2 | 2 3 3 | 1 5 4 | 0 Key: 1|2 = 12 2. **List all data points:** - From stem 0: 8 - From stem 1: 12, 17, 18, 19 - From stem 2: 22, 23 - From stem 3: 31, 35 - From stem 4: 40 So the data set is: $8, 12, 17, 18, 19, 22, 23, 31, 35, 40$ 3. **Count the number of data points:** There are $10$ numbers. 4. **Add all the numbers:** $$8 + 12 + 17 + 18 + 19 + 22 + 23 + 31 + 35 + 40 = 225$$ 5. **Calculate the mean:** $$\text{mean} = \frac{\text{sum of data}}{\text{number of data points}} = \frac{225}{10} = 22.5$$ **Final answer:** The mean of the data set is $22.5$.