We have indeterminateness of type
0/0,
i.e. limit for the numerator is
$$\lim_{x \to 3^+} \tan{\left(\pi x \right)} = 0$$
and limit for the denominator is
$$\lim_{x \to 3^+}\left(x - 3\right) = 0$$
Let's take derivatives of the numerator and denominator until we eliminate indeterninateness.
$$\lim_{x \to 3^+}\left(\frac{\tan{\left(\pi x \right)}}{x - 3}\right)$$
=
$$\lim_{x \to 3^+}\left(\frac{\frac{d}{d x} \tan{\left(\pi x \right)}}{\frac{d}{d x} \left(x - 3\right)}\right)$$
=
$$\lim_{x \to 3^+}\left(\pi \left(\tan^{2}{\left(\pi x \right)} + 1\right)\right)$$
=
$$\lim_{x \to 3^+} \pi$$
=
$$\lim_{x \to 3^+} \pi$$
=
$$\pi$$
It can be seen that we have applied Lopital's rule (we have taken derivatives with respect to the numerator and denominator) 1 time(s)