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 60000 - 40000 = 20000.

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 - 40000 = 20000).

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 - 50000 = 70000

x - 50000 + 50000 = 70000 + 50000

x - 0 = 120000

x = 120000

Check the answer by substituting the value of x (120000) back into the equation.

120000 - 50000 = 70000