You can use the Principle of Inclusion-Exclusion. Define
A = the event that you get A,K,Q of spades
B = the event that you get A,K,Q of hearts
C = the event that you get A,K,Q of diamonds
D = the event that you get A,K,Q of clubs
then
P(A \cup B \cup C \cup D) = P(A) + P(B) + P(C) + P(D) -...