Find the probability that the first chocolate with lemon flavour that Nell chooses is the $7\text{th}$ chocolate that she checks.
Find the probability that the first chocolate with lemon flavour that Nell chooses is after she has checked at least $6$ chocolates.
'Surprise' boxes of chocolates each have $15$ chocolates: $3$ lemon, $5$ orange and $7$ strawberry. Petra has a box of Surprise chocolates. She takes $3$ chocolates at random from the box. She eats each chocolate before taking the next one. Find the probability that none of Petra’s $3$ chocolates has orange flavour.
Find the probability that each of Petra’s $3$ chocolates has a different flavour.
Find the probability that at least $2$ of Petra’s $3$ chocolates have strawberry flavour given that none of them has orange flavour.