I can't believe the alternative method I just saw to calculate the average of two numbers:

```
I use the following:
(a+b)/2 = avrg(a,b)
(b+a)/2 = avrg(a,b)
Found someone using this:
a+((b-a)/2) = avrg(a,b)
b+((a-b)/2) = avrg(a,b)
```

How to calculate `avrg(a,b,c)`

using the second method? (e.g for the first one is `(a+b+c)/3`

)

How can I transform the first one into the second one, or otherwise find some proof they both are equally equal?