"We find the average."
Translation:Troviamo la media.
Because the mathematical average is "la media". When you say you find the average, you are making the sum of all the numbers and dividing by the numbers of addends. That's "fare la media" o "calcolare la media". You use "media" as a noun. When you are talking about an "average" guy/thing, you have to follow the gender of the noun it's referred to. Here "medio/a" is an adjective.
The average man: l'uomo medio
The average salary: lo stipendio medio
The average height: l'altezza media