WolframAlpha - WolframAlpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.
Cymath - Free Step-By-Step Solutions to algebra problems.
Microsoft Math Solver - Microsoft Math Solver is a simple to use math problem solving and calculator application that provides you with an extra edge to the students to make sure their solutions are right.
Photomath - Photomath is a mobile app that will give you the ability to test your equations through a simple calculator interface that will fully explain the solution in a step-by-step fashion. Read more about Photomath.
Symbolab - Step by step calculator
Physics-AST - Physics-AST is a physics problem solver that helps high school students to solve physics problem...