We have indeterminateness of type
-oo/-oo,
i.e. limit for the numerator is
$$\lim_{x \to -\infty}\left(x - \sin{\left(x \right)}\right) = -\infty$$
and limit for the denominator is
$$\lim_{x \to -\infty}\left(x - \tan{\left(x \right)}\right) = -\infty$$
Let's take derivatives of the numerator and denominator until we eliminate indeterninateness.
$$\lim_{x \to -\infty}\left(\frac{x - \sin{\left(x \right)}}{x - \tan{\left(x \right)}}\right)$$
=
$$\lim_{x \to -\infty}\left(\frac{\frac{d}{d x} \left(x - \sin{\left(x \right)}\right)}{\frac{d}{d x} \left(x - \tan{\left(x \right)}\right)}\right)$$
=
$$\lim_{x \to -\infty}\left(- \frac{1 - \cos{\left(x \right)}}{\tan^{2}{\left(x \right)}}\right)$$
=
$$\lim_{x \to -\infty}\left(\left(1 - \cos{\left(x \right)}\right) \left\langle -\infty, 0\right\rangle\right)$$
=
$$\lim_{x \to -\infty}\left(\left(1 - \cos{\left(x \right)}\right) \left\langle -\infty, 0\right\rangle\right)$$
=
$$1$$
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)