Subtraction is removing some objects from a group. The meaning of 5-3=2 is "Three objects are taken away from a group of five objects and two objects remain".

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