I've got a few used text books that are up for sale.
Covers mathematics - linear algebra, abstract math, discrete math, stats and calculus.
Elementary Linear Algebra with Applications (Anton, Rorres)
ISBN 0471851043, Published 1987
Asking: $5 (hardcover with light wear)
Introduction to Abstract Mathematics (Bond, Keane)
ISBN 0534959507, Published 1998 (1st edition)
Asking: $20 (hardcover, almost brand new)
Discrete Mathematics and Its Applications, 4th Edition (Rosen)
ISBN 0072899050, Published 1999
Asking: $10 (hardcover with wear along edges)
Introductory Statistics, 2nd Edition (Devore, Peck)
ISBN 0314027661, Published 1994
Asking: $15 (hardcover never used/ brand new)
Calculus, Combined Preliminary Edition (Mingarelli)
ISBN 0969888937, Published 1999
Asking: $5 OBO (paperback, well used with student notes made inside)
Located in Pickering / East Scarborough, but other arrangements may be possible.