Question 1042916

Don't know how to this equation.. can someone help me?
Solve the following equation for n

nC2 - 5{P(1/3n, 2)} + 1/3n = 9
<pre>The following quadratic ensues: {{{n^2 - 27n + 162 = 0}}}, which means that: {{{highlight_green(matrix(1,3, n = 9, or, n = 18))}}}