Binomial Theorem

[03myersd]

Just started doing binomial theorem and I am having a bit of a problem with my maths. The question is:

(n) = 10
(3)

(Basically one big bracket) and I need to get n.

This is what I have so far:

(n) = 10
(3)

n! / ((n-3)!*3!) = 10

n! / (n-3)! = 10 * 3!

n! / (n-3)! = 60

n(n-1)(n-2) = 60

n(n² - 2n - n + 3) = 6-

n(n² - 3n + 3) = 60

n³ - 3n² + 3n = 60

n³ - 3n² + 3n - 60 = 0

Then using a graphical calculator to get a root I am getting 4.9 (roughly) which I know must be wrong as it is wrong in the back of the book. What am I doing wrong or forgetting?