Question

What is the arithmetic mean of 2x and 2y?

Answer 1

Arithmetic mean is just a fancy word for 'average'
What's the average of 2x and 2y?

Answer 2

Average: You add all the terms and divide the total sum by the number of terms you added.
For instance, the average of 13, 17, 20, and 10, first, you add the four terms,
13 + 17 + 20 + 10 = 60
And then divide it by the number of terms, you had four, so
60/4 = 15
And that's their arithmetic mean (average).