# How do you number equations

I have an answer that has a number of equations. Within the text of the answer I just want to refer to the number of the equation. I saw it on an answer somewhere, but I can find such an answer now. What is the markup?

• Welcome to meta! We have a nice sandbox which is occasionally a good self-teaching guide, and almost always made dirty by our doodles. But you can find all things formatting there. – M.A.R. ಠ_ಠ Nov 7 '15 at 12:26

$2+2=4\tag{1}$