I have seen Your question many times:
Si tus pantalones se te caen ¿qué debes usar en la cintura?
This question translated means:
If your pants fall out, what should you wear at the waist?
Your answer to this question is:
Spanish: Si se cae los pantalones, debe usar un cinturón en la cintura.
English: If you drop your pants, you should wear a belt at the waist.
Hope I helped!!!!