Que or cuáles

Hola Jack

cual, cuales used as relative pronouns (which is this case: that, which...) are always used with the articles el cual, la cual, los cuales, las cuales, and no accent. 

When you use cuál and cuáles as such (no articles and with the accent) is when they are in an interrogative (direct or indirect) or exclamatory sentence:

In the sentence about the trousers, it is a relative pronoun referring to trousers:

Esos pantalones, los cuales he tenido...

These trousers, that/which I've had...

Saludos