Is it permissible to combine the Dhuhr and Asr prayers at the university, knowing that the distance between the university and home is 90 kilometers, and I return home before the time of the Asr prayer? And how many rak'ahs would be performed in this case?

It is permissible for a female traveler to combine and shorten the 'Asr and Dhuhr prayers, even if she knows that she will arrive before the 'Asr prayer time begins. However, it is preferable not to combine them in this case. For the concessions of travel to be permissible, the distance between the outskirts of the two cities (origin and destination) must be at least 83 km, and the traveler must not intend to reside in the destination city for four days or more (excluding the days of arrival and departure). Furthermore, it is not permissible for a woman to travel without a mahram (definition), and a woman who travels without a mahram is not allowed to avail herself of the concessions of travel.