Math Quiz project

This work isa beginner to intermediate C++ project, it asks user how much question he wants to solve, then ask about the level of exercises (hard, easy , meduim or mix), after that it asks the desired operation(addition, substruction, multiplication...) , then the questions display one after one and the user should solve them , if the answer for each question is correct, the screen displays good job, otherwise it prints incorrect and shows the correct one , after that it shows if the user has fail or pass this quiz and this is up to his total score