"Prove Fermat's Last Theorem."
Fermat's Last Theorem states that there are no three positive integers a, b, and c that satisfy the equation an + bn = cn for any integer value of n greater than 2.
This problem was famously unsolved for over 350 years until Andrew Wiles provided a proof in 1994. It involves advanced concepts from algebraic number theory, elliptic curves, and modular forms.