I have no head for numbers

When I were a lad, I never did understand algebra. It was a foreign concept to me, the idea that n could equal a number.
I remember on one occasion, I was presented with an algebra equation to solve, and could not make head nor tail of it.
Eventually, I turned to the boy sitting next to me, the class brainbox, Clark Clerk, and asked him for the answer,
"No," he said, sharply, but I persisted.
"Ah go on," I said.
Angrily he turned to me and said, "What part of no don't you understand?"
I said, "n."

Thank you algebra lovers!