How many three-digit numbers can be formed under each condition? (a) The leading digit cannot be zero.

(b) The leading digit cannot be zero and no repetition of digits is allowed.

(c) The leading digit cannot be zero and the number must be a multiple of 3.

(d) The number is at least 400.

well it says right there your brother is 13; "your age". so lets keep it simple. you are 13 years old and there is no way to put this into any kind of equation without wanting to tear your hair out. who came up with this?

turn 2 ft into 24 inches. then divide both numbers by 6 getting you 4 and 9. now make the fraction have a numerator of 4 and a denominator of 9, the answer is 4/9.