find the media of the following numbers. 15,8,3,5,611?

Answer 1

Did you mean the Median. That's easy. Arrange the numbers in order and find the one in the middle. So from 3, 5, 8, 15, 611 the answer would be 8.

The mean, i.e. the "average" (which is probably not what you meant) is calculated by adding up the numbers and dividing by the number of them.