WolframAlpha - WolframAlpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.
PhotoStudy - Stuck on a Math or Science Problem? Get Help From an Expert Tutor in Seconds!
TexMaths - TexMaths is an addon designed to provide LaTeX support into LibreOffice.
Mathway - Mathway is a freemium math solving app that helps you find the solutions to any math problem you can imagine.
iMathEQ Math Equation Editor - iMathEQ is a mathematics equation or formula editor.
Delta: Math helper - With Delta: Math helper, quickly solve any math problem with an algorithm. Save time checking your homework or studying for a test, it’s free!