Edexcel A level maths taken in England would be 3 A level exams, 2 are Pure Maths the third exam is comprised of a mechanics and a statistics section (you do both at the same time) that you'll find as separate papers on past paper web sites. You have to learn the Year 1 / AS content, it will be tested, but you don't take the AS exams, they are a separate, optional qualification.