Fractional equation
Each fractional equation always has one or more break terms with a variable $x$, which occurs in the denominator of at least one of these break terms.
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Hint
Most often, the variable is called $x$ in fractional equations. Note, however, that even equations with other letters can be fractional equations.
Example

Fractional equation
Equations where the variable is in the denominator
$\frac8x=4$
$\frac{5x}{3x+15}+2x=10$
$\frac{25}{4x+2}=\frac{4x}{4x+2}$ 
No fractional equations
There is no variable in the denominator
$\frac{1}{5}x+\frac{3}{4}x=8$
$\frac{2x}{2}=4$
$\frac{x+10}{4x8}$ (No equation, only one term)