This Viral Math Problem Stumped British Students - Can You Solve It?

There are n sweets in a bag. 6 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 n^2 – n – 90 = 0.

Blog post-http://mindyourdecisions.com/blog/2015/06/05/this-viral-math-problem-stumped-british-students-can-you-solve-i

Videohttps://www.youtube.com/watch?v=yBxDB12lqUc

Blog post-http://mindyourdecisions.com/blog/2015/06/05/this-viral-math-problem-stumped-british-students-can-you-solve-i

Videohttps://www.youtube.com/watch?v=yBxDB12lqUc