If it takes 25 minutes to fry a single burger, assuming only one burger can be made at a time, you must multiply the time per burger by how many burgers are made. So. 25(13) = 325 minutes <em>or</em> 5 hours and 25 minutes.
it's negative and positive and negative + positive is -ive or +ive but in this case they are in equal distance from the number line which makes the answer zero