For this question, why does the solution show the approach of taking combinations: i.e 4C3 * 8C3 / 12C6?
I used the approach that probability for passing (p) = 4/12 = 1/3 and probability of not passing (n) = 8/12 = 2/3
arranging them in straight line PPPNNN = 6!/ 3! 3! = 20. So , 20*(1/3)^3*(2/3)^3 = 0.21