A corollary to the fundamental theorem of calculus, compound interest (r is the rate, k the times it is calculated (the more the more accurate), n is the time passed), Einstein's mass-energy, Newton's law of gravitation (gravitational force in terms of masses and distance, with gamma the constant usually denoted by G), Uranium decay, quadratic formula, Ohm's law (it's electricity, voltage, resistance and current intensity), Pythagoras' Theorem, Einstein again, gravitation again, water, DNA blocks paired is the ATCG one.
They are all proved identities that are very useful , nothing to solve there, they are used a lot to solve problems though.
Bah you were quicker
