What fraction (part) of this hexagon is red?

If you said, "All of it." You are right... But, your answer isn't a fraction.
6 pieces out of 6 pieces are red... so, that's
.
This is the whole hexagon... It's
whole hexagon.
So,
is the same as
.

is like a magic
.
You'll see why later... You'll be able to do a LOT with magic 1's. Especially in Algebra.
Here are some more:

When the numerator equals the denominator, it's a magic 1.