There are n n\,n counters in a bag.
5 of the counters are red and the rest are blue.
Sarah takes a counter from the bag at random and does not replace it. She then takes another counter at random from the bag.
The probability that Sarah takes two blue counters is 37\displaystyle \frac{3}{7}73
Show that 2n2−37n+105=02n^2 - 37n + 105 = 02n2−37n+105=0
Find the value of nnn.