English for Today by Ganiu Abisoye Bamgbose (GAB)
You have to crack your brain to get this (nonstandard).
You have to rack your brain to get this (standard).
When you make a great effort to think of or remember something, you are racking your brain.
He’s the brain behind the project (nonstandard).
He’s the brains behind the project (standard). To be the person who plans and organizes something, especially something successful is to be the brains behind the thing.
GAB
