Tomamos como el límite
$$\lim_{x \to 0^+}\left(\frac{3 x^{2} + x}{4 x^{3} + \left(x + 10\right)}\right)$$
cambiamos
$$\lim_{x \to 0^+}\left(\frac{3 x^{2} + x}{4 x^{3} + \left(x + 10\right)}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{x \left(3 x + 1\right)}{4 x^{3} + x + 10}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{x \left(3 x + 1\right)}{4 x^{3} + x + 10}\right) = $$
$$\frac{0 \left(0 \cdot 3 + 1\right)}{4 \cdot 0^{3} + 10} = $$
= 0
Entonces la respuesta definitiva es:
$$\lim_{x \to 0^+}\left(\frac{3 x^{2} + x}{4 x^{3} + \left(x + 10\right)}\right) = 0$$