23: You should get
Since the outcome on the top is not clear, one cannot apply the usual l'Hospital rule right away, since it can be only used for indeterminate fractions (however, the more general version does work for "something over infinity"). In fact, since we know that eventually 3n prevails over n2, you can argue that this really is the "infinity over infinity" type and try the l'Hospital.
Some people might find the above solution incomplete, since you are using the powers scale in order to justify using the l'Hospital. How to complete it? Either you can actually prove that the numerator tends to infinity and thus justify your solution method - which is done by factoring out the leading power, or you can as well fit this whole problem to the box "polynomials and ratios with powers" and solve it by factoring out leading powers.
Note that by intuitive calculations, the leading terms are 3n in the numerator and 4n in the denominator, and the latter also prevails over the former. Thus it can be guessed right away that the whole fraction converges to zero.