What does | mean in math for example; |15|

What numbers are included in the set of integers? what numbers are not included?

Randy and trey take turns cleaning offices on the weekends. it takes randy at most 4 hours to clean the offices. it takes trey at most 6 hours to clean the offices. what is the greatest amount of time it would take them to clean the offices together? 2.4 hours 2.5 hours

Idon't want to fail summer school.the probabilities of contamination in medicine capsules due to the presence of heavy metals and different types of microbes are given in the table.the probability of capsule b having microbial contamination is (the same as, greater than, less than) the probability of capsule d having it.