Question

In a box, there are black pens, red pens and green pens
the ratio of black pens to not black pens is 9:11
the ratio of green pens to not green pens is 3:5
fins the ratio of black pens to red pens to green pens

Answer 1

What do we know?

There are 9 black pens and 3 green pens.

What else do we know?

We know that 11 of the pens aren't black, and 5 of them aren't green.

Black pens (9) : red pens (6) : green pens (3)

How'd I get 6?

If 11 pens aren't black, they had to be green, but 5 of them weren't green. So, I subtracted 11 from 5 to get 6 red pens.

I hope that makes sense.

Final answer:

9:6:3

WARNING: I could be wrong as I'm not fully sure, but this is what I think.