This is a Yu-Gi-Oh Duel Links question. It is a mobile application that allows you to duel other players with digital cards.
Only 2 copies of Card A exist in the 20 card deck.
Only 3 copies of Card B exist in the 20 card deck.
Card B can search for Card A.
What is the equation to determine the probability/likelihood of seeing Card A in a 20 card deck?
For example Card A is your win condition, and subsequentlly, drawing card B is also your win condition (since Card B searches for Card A). Drawing any copy of Card A or Card B in your opening hand is your win Condition.
You can only draw 4 cards in your opening hand.
For simplicity, the sample size thresholds can be [100] [1,000] [10,000]
Let X be the event that either card A or card B is drawn. Then, P(x) = $2/20 + 3/20 = 1/4$