One bow = 4 cheers.
4 cheers = 8 hops.
8 hops = 24 twitches.
24 twitches = 240 claps.
240/7 = 34.28
Since you can't have a fraction of a person, there must have been at least 35 people.
BONUS!
100 people = 700 claps.
700 claps = 70 twitches.
70 twitches = 23 hops. (You can't have .3 of a hop)
23 hops = 11 cheers. (You can't have half of a cheer)
11 cheers = 2 bows. (You can't have three-quarters of a bow)
At most, they will bow twice.