You want to know how to approach difficult and simple exam problems.
When given an exam, take a quick glance at the entire thing to determine what’s involved. Start with the hardest problem. If you get stuck on it for more than two minutes, switch to an easier problem. Continue to solve what you can and then come back to the difficult one.
This strategy can be employed to practice exercises as well. When you begin with a hard problem, your brain loads your focused mode. When you switch attention away from it, your diffused mode kicks in. Turning to an easier problem allows different parts of your brain to work simultaneously on different thoughts.