I want to compute a)The probability of getting at least one 3 in the rollings of 6 dice b) The probability of getting at least two '3's in the rollings of 12 dice. c)The probability of getting at least three '3's in the rollings of 18 dice.

Solution:- I computed the probability for a)=$\frac{3906}{46656}$

b)$\frac{\frac{1(5^{11}-1)}{4}}{6^{12}}$

c)$\frac{\frac{1(5^{16}-1)}{4}}{6^{18}}$

Are these answers correct?