Math Help Please?!?

1/13

That's (12/13)(4/51) +(1/13)(3/51).
The prob when missing card is not a jack plus when it is.

4/52 = 1/13. Since we have no information about the identity of the lost card, it makes no difference that a card has been lost.

The lost card is random. So is the one card drawn. The probability is the same as a random card from a full deck, 1/13. The fact that a card is lost is immaterial when you have no information about it.

This is similar to the problem: The deck is shuffled and the top card discarded. What's the probability that the next card is an ace. \

If you analyze the problem by assuming the lost card is or is not an ace, you get the same answer.
If it's an ace (prob = 1/13), then the probability is 3/51.
If it's not an ace (prob = 12/13, then the probability is 4/51.

1/13 x 3/51 + 12/13 x 4/51 = (3 + 48)/(13 X 51) = 1/13

Ptot = Probability if the lost card is an ace (Pa) + Probability if the lost card is not an ace (Pb)

Pa = 4/52*3/51
Pb = 48/52*4/51

Pa + Pb you will find it equals 1/13, thus you can conclude that it makes no difference whether the lost card is an ace or not as suggested by one of the answers.

Ptot = 1/13