Anya and Ben each have a bag containing \(3\) red counters, \(5\) blue counters and \(7\) yellow counters.
Anya takes \(2\) counters at random from her bag without replacement. Find the probability that the \(2\) counters are of different colours.[3]
Ben takes counters at random from his bag one at a time without replacement. The probability that his first red counter is the \(n\)th counter he takes is \(\frac{36}{455}\). Find the value of \(n\).[2]