Is there notation for what is essentially when, for the situation, for example:
In the situation when x is 2, y is 21t (edited)
Sorry for being brief; if it lacks clarity, please leave a comment and I will amend it
Edit:
It's to keep my math notes tidy when I'm asked to write the acceleration when time is 0; I have to write this as words though I feel it's sloppy and I'm wondering if there's notation for this situation