Answer:
25 years
Explanation:
To find the mean you need to find the sum of all numbers and divide by the number of terms there are.
In this case you would need to multiply the mean ages by the number of people used to find the mean:
35 * 3 = 105
23 * 12 = 276
Then add the total ages together:
105 + 276 = 381
Then divide by the number of total people in the office:
12 + 3 = 15
381/15 = 25.4
rounded to 25