How do I help my little brother with negative numbers? He doesn't understand when it is positive and when it is negative.

Answer 1

You can show him a number line. This is an excellent site.

http://www.mathsisfun.com/positive-negative-integers.html

If your brother understands money, you can use a loan as an example. For instance, if borrows a dollar from you, he has negative $1. because he owes it to you.

Answer 2

This is how I remember arithmatic with negative numbers:

Addition/Subtraction: if the signs are the same you add, answer takes sign of largest number; if the signs are different you subtract, answer takes sign of largest number (this is for calculation with two numbers)

Multiplication/Division: if the signs are the same, the answer is positive; if the signs are different, the answer is negative (this is for calculation with two numbers)