There are numerous mathematical relationships that have been established in science, finance and other areas. Examples include the relationship between force and acceleration, conversion of centimeters to inches, and determining the payments on a loan with a given interest rate.

The purpose of Algebra is to make it easy to state the relationship by using letters to represent entities as a form of shorthand. The relationship is then called an equation. Algebra then allows you to substitute values for entities in order to determine the value of other items. Finally, you can manipulate the equations to solve for the various items or unknown quantities.