This book contains a large variety of basic aspects in elementary mathematics as well as a long list of original exercises and problems created by the authors, some of these published in famous mathematical magazines such as American Mathematical Monthly, Crux Mathematicorum, The Pentagon Journal, College Mathematical Journal, SSMA Magazine, MathProblems Journal, Mathematics Magazine, La Gaceta de la RSME, Romanian Mathematical Magazine. A special mention is deserved by the only Interactive Mathematical Journal from Romania: RMM , with over 4.600.000 visitors in 2 years, where the authors have a large contribution as proposers and solvers. Autori: George Apostolopoulos; Daniel Sitaru