Why does asking for fib(6) — whose answer is just 8 — trigger fifteen separate calls, and where in the call tree does the naive version redo work it already finished?
Short drills on what this video just taught. Write the code, run the checks, and reveal the answer only if you are stuck.
You are handed two facts and nothing else: fib(7) is 13 and fib(8) is 21. Working only from the rule fib(n) = fib(n-1) + fib(n-2), walk the sequence forward until you reach fib(10).
The two values you were handed are already assigned for you. Assign the value of fib(10) to fib10. Do not look the sequence up — derive it.