I believe it's this;
[table="width: 715]
[tr]
[td]
[/td]
[td]
[/td]
[/tr][/table]
HTML:
[table="width: 715]
[tr]
[td][spoiler=left][/spoiler][/td]
[td][spoiler=right][/spoiler][/td]
[/tr][/table]
There's probably another way to change the length of the spoilers, but that's just the one I know of.