If 1/2 hour naomi stretches her neck; every 1/3 hour she stretches her legs; and every 1/6 hour she stretches her ams. which parts of her body will naomi stretch when 2/3 hour has passed

Neck: In 2/3 of an hour Naomi will stretch her neck one (there's not enough time for two neck stretches, that would require an hour).
Legs: In 2/3 of an hour, she will stretch her legs twice (1 stretch every 1/3 of an hour for 2/3 of an hour equals 2).
Arms: In 2/3 of an hour she will stretch her arm four times (2/3 divided by 1/6 equals 4). 

Total stretches: 1 neck stretch, 2 legs stretches, and 4 arms stretches.