Get (one's) brain in gear phrase
The noun "brain" can be replaced by "head" or "mind".
To begin using your mind to think sensibly about something to deal with it.
When the teacher said that anyone solving the maths puzzle would be rewarded, every student got their brain in gear.
After getting my brain in gear for a while, I realized that this equation wasn't as difficult as it looks.
Why did you give up solving it so early? You don't even get your brain in gear!
Is the result worth the effort we have to put into it?
To take something into consideration in a thorough way
To think or consider something seriously
to say or reply something without having thought about it or knowing whether it is corect
The verb "get" must be conjugated according to its tense.
The origin of this phrase is not clear.