An equation is a mathematical statement such that the expression on the left side of the equals sign (=) has the same value as the expression on the right side. An example of an equation is 6000 - 4000 = 2000.

One of the terms in an equation may not be know and needs to be determined. Often this unknown term is represented by a letter such as x. (e.g. x - 4000 = 2000).

The solution of an equation is finding the value of the unknown x. To find the value of x we can use the additive equation property which says: The two sides of an equation remain equal if the same number is added to each side.

Example:
x - 5000 = 7000
x - 5000 + 5000 = 7000 + 5000
x - 0 = 12000
x = 12000
Check the answer by substituting the value of x (12000) back into the equation.
12000 - 5000 = 7000