Answer:
1/6
Step-by-step explanation:
There are 4 cards, 2 of which are primes
P(prime) =number of primes/total
= 2/4 = 1/2
Keep the card, now we have 3 cards, 1 of which is a prime
P(prime) =number of primes/total
= 1/3
P(prime, keep , prime) = 1/2*1/3 = 1/6