Question

insert two dashes where needed. at the international dragon boat carnival in hong kong, hundreds of teams from around the world some five thousand paddlers in total race to the sound of beating drums.

Explanation:

The phrase "some five thousand paddlers" is an appositive - like addition to provide more information about the "hundreds of teams". Dashes are used to set off this non - essential but clarifying information.

Answer:

At the International Dragon Boat Carnival in Hong Kong, hundreds of teams from around the world - some five thousand paddlers in total - race to the sound of beating drums.