===== Answer =====

one solution is 4 total students with 3 having blue eyes but there is more than one answer.

For the general solution, let //x// be the total number of students and let //b// be the number of students with blue eyes.

//P(2b) = .5//

//P(2b) = b/x * (b-1)/(x-1)// with //b ≤ x// and //b,x ∈ **Z**<sup>+</sup>//

This general solution can be solved numerically, giving 4 answers is you restrict x to be less than 100000.