numbers gives a numerical solution; for example, gives (that is, ), and gives .

The distinction between known variables and unknown variables is generally made in the statement of the problem, by phrases such as "an equation in and ", or "solve for and ", which indicate the unknowns, here and .However, it is common to reserve , , , ... to denote the unknowns, and to use , , , ... to denote the known variables, which are often called parameters. This is typically the case when considering polynomial equations,