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 6 - 4 = 2.

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 - 4 = 2).

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 - 5 = 7

x - 5 + 5 = 7 + 5

x - 0 = 12

x = 12

Check the answer by substituting the value of x (12) back into the equation.

12 - 5 = 7