For $(a)$, we have $$\mathbb P(A) = \frac{\frac{52!}{(52-6)!}}{52^6} = \frac{8808975}{11881376} \approx 0.74141.$$
For $(b)$, this is simply the complementary probability: $$ 1 - \mathbb P(A) = \frac{3072401}{11881376}\approx 0.2585897. $$
For $(a)$, we have $$\mathbb P(A) = \frac{\frac{52!}{(52-6)!}}{52^6} = \frac{8808975}{11881376} \approx 0.74141.$$
For $(b)$, this is simply the complementary probability: $$ 1 - \mathbb P(A) = \frac{3072401}{11881376}\approx 0.2585897. $$