1. I learned that an effective method to solve A complicated problem is to use Top-down approaches to divide it into subsystems that are easy to be understood. "subsystems that are easy to understand" or "that are easily understood". 2.I mainly learned three ways to tackle problems from this experience. Firstly, fully understand the problem. Firstly, + a complete sentence Some suggestions: "Firstly, it is important to fully understand the problem." "Firstly, full understanding of the problem is essential." "Firstly, I need to fully understand the problem."