A literal equation is an equation that is comprised mostly or entirely of variables, usually representing known quantities. $$A=\pi r^2{a}^2+b^2=c^{2}E=m{c}^2$$ The three literal equations above are the area of a circle, the Pythagorean Theorem and Einstein's mass-energy equivalence. Literal equations can be solved, using the Properties of Equality to isolate a variable.