Your question is Analyzing Recursive Time Complexity. 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).
Explain Big O notation, then walk through how you would analyze the time complexity of a recursive algorithm. What do you look at in the recurrence, and how do you reason about both time and space?