meh...i don't know what has been answered so ill just answer them all...
Paul is 20 years old in 1980, but only 15 years old in 1985. How is this possible?
B.C time
What has roots that nobody sees, and is taller than trees? Up, up it goes, and yet it never grows.
Mountains
What's black when you get it, Red when you use it, and white when you're all through with it?
Charcoal
How can you drop a raw egg onto a concrete floor without cracking it?
Cracking concrete is really hard
How can you lift an elephant with one hand?
Where in the would you have seen a elephant with one hand
How can a man go eight days without sleep?
easy, I will sleep at night
What always runs but never walks, often murmurs, never talks, has a bed but never sleeps, has a mouth but never eats?
a river
What is in seasons, seconds, centuries and minutes but not in decades, years or days?
the letter "n"
The more you have of it, the less you see. What is it?
Darkness
What starts with a T, ends with a T, and has "T" in it?
teapot