Solution:

three positive numbers are 1 2 & 3

1 x 2 x 3 = 6
1 + 2 + 3 = 6

Solution:

A man, who crawls on all fours as a baby, walks on two legs as an adult, and walks with a cane in old age.

Of course morning, noon, and night are metaphors for the times in a man's (person's) life. Such metaphors are common in riddles. There were two Thebes, apparently this Thebes was the one in Greece. And this Sphinx was apparently not the one at Giza, in Egypt.

Solution:

Only twenty-three people need be in the room, a surprisingly small number. The probability that there will not be two matching birthdays is then, ignoring leap years, 365x364x363x...x343/365 over 23 which is approximately 0.493. this is less than half, and therefore the probability that a pair occurs is greater than 50-50. With as few as fourteen people in the room the chances are better than 50-50 that a pair will have birthdays on the same day or on consecutive days.

Solution:

Suicide

Solution:

Throw the ball straight up in the air.

Solution:

At that moment, the time, and day could be written as '12:34 5/6/78'

Solution:

We can calculate out how many days there will be for the 13th on each month if we count from the beginning of the year (January 1). Then we divide total days by 7 to get the remainders. We also need to consider the leap year. Through the whole year we had all kinds of remainders, from 0 to 6. The minimum of occurence for all the unique remainders was 1. It means that we have at least one Friday on 13th. In a regular year, the best chance you can get 3 Fridays on 13th, which are in February, March and December because the remainders of these 3 months are 2. In a leap year, the best chance you also can get 3 Fridays on 13th, which are in January, April and July because the remainders of these 3 months are 6.