This textbook is aimed at students in the third year of secondary education, economics and management section. It has been produced in accordance with the new syllabus (applicable from September 2007). This handbook has a unifying concept: it is a continuum whose various parts refer to each other. Its aim is not to be exhaustive, but to be educational and explanatory, so that the essentials are clearly understood and a wider field is opened up. Our main objectives are to- To consolidate the knowledge already acquired in 2nd and 4th year;- Motivate students by enabling them to apply their knowledge in practical situations;- Encourage students to appreciate the value and limitations of the information available for decision-making. This handbook contains six chapters that follow the same approach.In writing this handbook, we have done our best to produce a pleasant and attractive book that will enable students to approach their end-of-year exams in excellent conditions.