Thanks a lot

Really, but there's no option provide..

Here' the solution, really confuse

Prob. of a randomly selected person to have NOT been born in a leap yr = 3/4

Take 2 people, probability that none of them was born in a leap = 3/4*3/4 = 9/16. The probability at least one born in leap = 1- 9/16 = 7/16 < 0.5

Take 3 people, probability that none born in leap year = 3/4*3/4*3/4 = 27/64.

The probability that at least one born = 1 - 27/64 = 37/64 > 0.5

Thus min 3 people are needed.