Dear Ali
Remember! Math is not like other subjects. It can't be learnt by heart. It has to do with our brain functioning. You had better do Math problems with full concentration. Try not to skip any step of the procedure. In each chapter, the concept is explained initially and then they give examples to reinforce the concept. Once the concept is clear, you need not to do all the sums. You will be able to solve any problem even that is out of the exercise.