A literal equation is an equation that has more than one variable. In math, we work with literal equations all the time. For example, the slope–intercept form of a line is a literal equation: y = mx+b. This is because it has more than one variable.
Formulas are common literal equations. Formulas relate variables together. For example, we can use a formula to relate the length and width of a rectangle to its area. We can rewrite formulas to create expressions for other variables in the equation. For example:

Formula for the area of a rectangle  

Divide by w; expression for length 


Divide by l, expression for width 
We can rewrite literal equations to express other variables by apply inverse operations. More specifically, we look at what operations are being applied to the variable we wish to isolate, as well as in what order they are being applied. To isolate the variable, we apply the inverse operations in reverse order. This is shown below with several common formulas:

Formula for the area of a circle  

Divide both sides by 


Take square root of both sides 

 

Formula for distance, rate, and time  

Divide both sides by t  
 

Formula for distance, rate, and time  

Divide both sides by r  
 

Pythagorean Theorem  

Subtract from both sides  

Take square root of both sides  
 

Pythagorean Theorem  

Subtract from both sides  

Take square root of both sides 