Two trains are on the same railroad track; one is headed east the other west, they both leave the station at 1:00 and are travelling at the same speed. Yet they didn't crash into each other. How can this be?

They went at the same time but one went at 1:00 in the afternoon and one went at 1:00 in the morning.

How do you write 23 using only the number 2?

34 using only the number 3?

56 using only the number 5?

100 using only the number 9?