"Oh, I don't know about that," and Miss Cox opened the book at the first page and read as follows: "'In Algebra, the operations of Arithmetic are abridged and generalized by means of Symbols.' That appeals to the imagination somewhat, I think. 'Symbols which represent numbers.' Just that word 'Symbol' sets me to dreaming. Arithmetic is the prose of Mathematics where everything is stated and nothing left to the imagination, but Algebra is very different. 'Known Numbers are usually represented by the first letters of the alphabet, as a, b, c. Unknown Numbers, or those whose values are to be determined, are usually represented by the last letters of the alphabet, as x, y, z.' The unknown numbers,--the mysterious numbers,--for what is unknown is in a measure mysterious and what is mysterious is romantic or poetic. That is the way I think of it. In working your Algebra, don't just look at it as hard, dry facts to be mastered, but let x, y, z be the Great Unknown that you are to find. Let the problem be a plot that you are to unravel as Poe did 'The Gold Bug.'"