Question

add a comma or semicolon if needed. otherwise, submit the text without any additional punctuation. when deep blue, a chess - playing computer system, beat russian grandmaster garry kasparov in 1996 the event marked the first time a computer had defeated a world champion in a tournament.

Explanation:

The clause "a chess - playing computer system" is a non - essential appositive phrase. Non - essential appositive phrases are set off by commas. After the year "1996", a comma is needed to separate the introductory clause "When Deep Blue, a chess - playing computer system, beat Russian grandmaster Garry Kasparov in 1996" from the main clause "the event marked the first time a computer had defeated a world champion in a tournament".

Answer:

When Deep Blue, a chess - playing computer system, beat Russian grandmaster Garry Kasparov in 1996, the event marked the first time a computer had defeated a world champion in a tournament.