Video

Systems of equations: trolls, tolls (1 of 2) (Full video)

Description: A troll forces us to use algebra to figure out the make-up of his currency. We end up setting up a system of equations. Created by Sal Khan. And he says, well, I'm a reasonable troll. And when you look a little bit more carefully, you see that there actually was a sign there that says $5 toll to cross the bridge. And so the troll says, well, you can't cross.

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