What is the solution regarding the immodestly dressed women in a mixed-gender study environment that does not respect Islamic particularities?

The solution lies in lowering your gaze and refraining from looking at what Allah has forbidden, occupying yourself with beneficial matters, and frequently engaging in remembrance (dhikr) and reciting the Quran. Young people should apply the Prophet's (peace be upon him) advice: "O assembly of youth, whoever among you can afford to marry, let him do so, for it is more effective in lowering the gaze and guarding one's chastity. And whoever cannot afford it, let him fast, for it will be a shield for him." If you are able to marry, then hasten to do so. If you are not able, then you must fast, perform acts of obedience, and supplicate. If the school is bad, with immodesty and forbidden acts, try to transfer from it. If you cannot find another, then attend only what is necessary, avoid looking at and speaking with women and sitting near them, and strive to keep good company.