Simplify the following text for a Grade 9 native English-speaking person.
Original: The version of rugby union is very popular , with notable competitions including the IRB Sevens World Series and the Rugby World Cup Sevens . It is also played at events such as the Commonwealth Games and rugby league has also adopted the sevens format .
Simplified: Three of the best known sevens competitions are the Hong Kong Sevens , Wellington Sevens , and the Dubai Sevens which now make up part of the IRB Sevens World Series .