One person can do a certain job in fifteen minutes, and another person can do the same job in thirty minutes. how many minutes will it take them to do the job together?

What is the result of the following division?

For the inequality |c| < |d| to be true, which of the following must be true?

Arace is 10 kilometers long. markers will be placed at the beginning and end of the race course and at each 500 meter mark. how many markers are needed to mark the course for the race?