Pippa has a box containing $$\(N\)$$ pens. There are only black pens and red pens in the box. The number of black pens in the box is 3 more than the number of red pens. Pippa is going to take at random 2 pens from the box. The probability that she will take a black pen followed by a red pen is $$\(\frac{9}{35}\)$$ Find the possible values of $$\(N\)$$. Show clear algebraic working.

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