Will the sum of the three even numbers be odd or even?

Even.

Step-by-step explanation:

They will be even.

All even numbers, by definition, are divisible by 2.

We can write 3 even numbers as 2m, 2n and 2p.

So the sum = 2m + 2n + 2p

= 2 (m + n + p).

This proves it because the sum is a multiple of 2 and must be even.