Math is for Blockers (Plane) is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Whenever a nontoken creature attacks, exile it. Return it to the battlefield under its owner's control tapped and attacking at the beginning of that player's next declare attackers step. Whenever chaos ensues, goad target creature. (Until your next turn, It attacks each combat if able and attacks a player other than you if able.)