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 - 2 - (- 6) = 4.

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. - 2 + x = 4).

The solution of an equation is finding the value of the unknown x. To find the value of x we can use the subtractive equation property which says: The two sides of an equation remain equal if the same number is subtracted from each side. We may also 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 - (- 5) = 4
x + 5 = 4
x + 5 - 5 = 4 - 5
x + 0 = - 1
x = - 1
Check the answer by substituting the answer ( - 1) back into the equation.
- 1 - ( - 5) = 4