Answer
Undefined solution for $m=3$
Work Step by Step
Given: $\dfrac{m}{m-3}+\dfrac{1}{4}=\dfrac{m}{m-3}$
When he puts $m=3$, the equation does not satisfied which makes the denominator equals to $0$.
That is,
$\dfrac{m}{m-3}+\dfrac{1}{4}=\dfrac{m}{m-3}$
$\dfrac{3}{3-3}+\dfrac{1}{4}=\dfrac{3}{3-3}$
$\dfrac{3}{0}+\dfrac{1}{4}=\dfrac{3}{0}$
This represents an undefined solution for $m=3$
