Explanation:
a probability is always the ratio of
desired cases / totally possible cases
in our case, where we pull one card out of 52, the totally possible cases are, of course, 52.
now, we need to find the number of desired cases.
8 of diamonds is pulled.
well, that is one specific card. no other card matches this criteria. so, the probability is
1/52 = 0.019230769... ≈ 0.019
heart or spade is selected.
we have 13 cards of heart.
we have 13 cards of spades.
there is no overlap, so, together they are 26.
the probably is then
26/52 = 1/2 = 0.5
number smaller than 7 is pulled.
"smaller than 7" means 1..6.
that means 6 cards of each of the 4 suits = 24 cards.
the probability is then
24/52 = 6/13 = 0.461538462... ≈ 0.462