To find the mean (also called the average) of a set of numbers, you follow these steps:

1. Sum all the numbers in the set.
2. Divide the sum by the total number of values in the set.

The formula is:

$\text{Mean} = \frac{\text{Sum of all values}}{\text{Number of values}}$

Example:

Suppose you have the numbers: 5, 10, 15, and 20.

1. Sum the numbers: $5 + 10 + 15 + 20 = 50$
2. Divide the sum by the number of values (4 in this case):

$\text{Mean} = \frac{50}{4} = 12.5$

So, the mean of these numbers is 12.5.

Do you need help with a specific set of numbers or more examples?