This is a binomial distribution with p= 0.2= 1/5, q= 0.8= 4/5. "At least 5" in a group of 6 is "either 5 or 6" so the probability is [tex]\begin{pmatrix}6 \\ 5 \end{pmatrix} (0.2)^5(0.
+ \begin{pmatrix}6 \\ 6 \end{pmatrix} (0.2)^6= 6(0.2)^5(0.
+ (0.2)^6[/tex].