en.wikipedia.org/wiki/Equation

In mathematics, an equation is a statement of an equality containing one or more
variables. Solving the equation consists of determining which values of the ...

www.sosmath.com/algebra/solve/solve0/solve0.html

This sections illustrates the process of solving equations of various forms. It also
shows you how to check your answer three different ways: algebraically, ...

www.mathway.com/

Offers tutorials on the basics, word problems, and systems of equations.

www.mathpapa.com/algebra-calculator.html

If you would like to create your own math expressions, here are some ... Read the
full tutorial to learn how to graph equations and check your algebra homework.

www.wolframalpha.com/examples/Math.html

Math calculators & answers: elementary math, algebra, calculus, geometry,
number theory, discrete & applied math, ... solve an ordinary differential equation.

www.khanacademy.org/math/cc-eighth-grade-math/cc-8th-solving-equations

Linear equations can either have a single solution, infinite solutions, or no
solutions. Learn how to determine the number of solutions to a given equation,
and ...

www.khanacademy.org/math/algebra-basics/alg-basics-linear-equations-and-inequalities

Solve equations by adding/subtracting numbers from both sides, or by multiplying
/dividing both .... Learn how to solve more complex (mathematical) inequalities.

www.mathsisfun.com/algebra/equation-formula.html

Math explained in easy language, plus puzzles, games, quizzes, worksheets ...
That equations says: what is on the left (x + 2) is equal to what is on the right (6).

www.coolmath.com/algebra/12-2x2-systems-of-equations/03-solving-by-elimination-addition-01

If we add the two equations -- straight down, those x critters are going to drop
right out! Just add "like terms" and drag the "=" down to: ( 2x + 3y = 20 ) + ( -2x + y
...

www.coolmath.com/prealgebra/16-intro-to-solving-equations/01-solving-equations-balance-01-177

This prealgebra lesson explains why equations need to stay balanced as you
solve them.