There are websites that can answer algebra, geometry, trigonometry, calculus, statistics and finite math. Mathway is a robust math program online that preforms many different functions including simplifying and evaluating problems.
Mathway's site also has an extensive library of examples detailing concepts and theories about all the kinds of mathematics their service offers resources for. Their database has tutorials for basic math at one end and chemistry and statistics on the advanced side.
There are also phone apps that can solve and explain the work involved by taking a picture of a math problem. PhotoMath, offers an educational tool that solves math problems and then gives a step-by-step explanation of how the answer was reached.