Your question is Heavier Ball in Two Weighings. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
You have nine balls, all identical in weight except for one that is heavier, and a balancing scale. If you can only use the scale twice, how do you identify the heavy ball?