He sold about <span>80% of his tickets</span>
The rational root theorem states that the rational roots of a polynomial can only be in the form p/q, where p divides the constant term, and q divides the leading term.
In your case, both the leading term 5 and the constant term 11 are primes, so their only divisors are 1 and themselves.
So, the only feasible solutions are

For the record, in this case, none of the feasible solutions are actually a root of the polynomial.
1:5=1/5
1/5=20/100
20/100= 20%
20% of bag is pink marbles