Can someone PLEASE help? only if you know how!

answer has to be in simplest radical form

If a and −a are numbers on the number line, which expression must give the distance between them? a) 0 b) a c) |2a| d) |a|

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

Sections of prefabricated wood are each 5 1/3 feet long. how long are 7 1/2 sections placed end to end?