If , and , then P(B | A) is equal to

A die is tossed twice. A ‘success’ is getting an even number on a toss. Find the variance of the number of successes.

There are 5 cards numbered 1 to 5, one number on one card. Two cards are drawn at random without replacement. Let X denote the sum of the numbers on two cards drawn. Find the mean and variance of X.

If P(A ∩ B) = 7|10 and P(B) = 17|20, then P(A|B) equals

If P(A) = 3|10, P(B) = 2|5 and P(A ∪ B) = 3|5, then P(B|A) + P(A|B) equals