"This whole balance thinga-magig seems really familiar. It reminds me of equations!

"First, I didn't know how many cookies were in a bag. So that's the unknown, like a variable!"

x=?

"And there are two on one side plus 3 additional cookies and 1 on the other side plus 8 additional cookies."

2x + 3 = x + 8

"And the balance shows they're equal."