Divide the numbers like you would divide two positive numbers using a calculator or long division. Then, when you divide two numbers, and one is positive, and one is negative, the result is negative.
When you divide a negative and a positive, you don't have to worry about the negative that much. Just divide like normal, and then add the negative at the end. However, if you divide a negative by a negative, it's double negative, and therefore positive. So in the case of -19 / 13, the answer would be negative.
