If you're not sure exactly what you're looking for, you may find it useful to browse the Library shelves at the following call number locations:
QA 9.54 Mathematical proof
QA 43 Mathematics--Problems, exercises, etc. (including competitions)
QA 95 Mathematical recreations
QA 101-QA 141.8 Elementary mathematics. Arithmetic
QA 150-QA 272.5 Algebra
QA 273-QA 280 Probabilities. Mathematical statistics
QA 299.6-QA 433 Analysis
QA 304-QA 306 Differential calculus
QA 308-QA 313 Integral calculus
QA 440-QA 699 Geometry. Trigonometry. Topology
T 57.74-T 57.78 Linear programming
TA 330-TA 347 Engineering mathematics
HF 5691-HF 5716 Business mathematics