The arithmetic mean of 3a, 3b, 3c is __________

Answer

To find the arithmetic mean of the numbers 3a, 3b, and 3c, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Numbers**: The numbers we need to find the arithmetic mean for are 3a, 3b, and 3c.

2. **Formula for Arithmetic Mean**: The arithmetic mean (or average) is calculated using the formula:
\[ \text{Arithmetic Mean} = \frac{\text{Sum of all values}}{\text{Number of values}} \]

3. **Calculate the Sum of the Values**:
- The sum of the values 3a, 3b, and 3c is:
\[ 3a + 3b + 3c \]

4. **Factor Out Common Terms**:
- We can factor out the common term (3) from the sum:
\[ 3(a + b + c) \]

5. **Count the Number of Values**:
- There are 3 values (3a, 3b, and 3c).

6. **Substitute into the Formula**:
- Now, substitute the sum and the number of values into the arithmetic mean formula:
\[ \text{Arithmetic Mean} = \frac{3(a + b + c)}{3} \]

7. **Simplify the Expression**:
- The 3 in the numerator and the 3 in the denominator cancel out:
\[ \text{Arithmetic Mean} = a + b + c \]

### Final Answer:
The arithmetic mean of 3a, 3b, and 3c is:
\[ \boxed{a + b + c} \]