9567 + 1085 = 10652

A bar of soap.

You're looking sharp.

A railing

He was using Roman numerals: V + V = X

Pumps.

43 is the largest number that cannot be made using the numbers 6, 9, and 20.

Every natural number is member of one of the following six series:

0, 6, 12, 18, ...
1, 7, 13, 19, ...
2, 8, 14, 20, ...
3, 9, 15, 21, ...
4, 10, 16, 22, ...
5, 11, 17, 23, ...
If for a number in one of these series holds that it can be made using the numbers 6, 9, and 20, then this also holds for all subsequent numbers in the series (by adding a multiple of 6).

To find out what the largest number is that cannot be made using the numbers 6, 9, and 20, we therefore only need to know, for every series, what the smallest number is that can be made in that way.

In the series 0, 6, 12, 18, ... the smallest number that can be made is 0, so there is no number that cannot be made.
In the series 1, 7, 13, 19, ... the smallest number that can be made is 49 (20+20+9), so 43 is the largest number that cannot be made.
In the series 2, 8, 14, 20, ... the smallest number that can be made is 20, so 14 is the largest number that cannot be made.
In the series 3, 9, 15, 21, ... the smallest number that can be made is 9, so 3 is the largest number that cannot be made.
In the series 4, 10, 16, 22, ... the smallest number that can be made is 40 (20+20), so 34 is the largest number that cannot be made.
In the series 5, 11, 17, 23, ... the smallest number that can be made is 29 (20+9), so 23 is the largest number that cannot be made.

An antique!

Pencil lead.

One of the ten people had the key to the room. He unlocked the door, except there was nobody outside of the room.

A junk yard (3 feet = 1 yard).

The answer to this admittedly lame riddle is, “No.” The reason is that the question at the very end asks if you can guess the riddle and there is nothing that satisfies the requirements above. Some say that pressure is the answer, but they can’t explain how it turns polar bears white or pancakes brown. Nothing turns polar bears white, any more than something turns a white person white, and heat makes pancakes brown, not pressure.