Students in UK protest against difficult GCSE Maths question

Just came across this piece of news posted a while back by the Guardian: Student protest against ‘unfair’ GCSE maths question goes viral

There are n sweets in a bag. Six of the sweets are orange. The rest of the sweets are yellow. Hannah takes a random sweet from the bag. She eats the sweet. Hannah then takes at random another sweet from the bag. She eats the sweet. The probability that Hannah eats two orange sweets is 1/3. Show that n²-n-90=0.

In Singapore, a grade B student will be expected to solve this kind of questions.

If you want the solution:

The probability of eating 1 orange sweet is 6/n, two in a row is 6/n * 5/(n-1) = 1/3 in the question.

Massaging the above will give n²-n-90=0.