How do you say "it is made of leather." in spanish?

Does anyone know what my spanish teacher means by this? i need to use plural forms of the verb ser. and she asked me to use a couple of adjectives to describe the boys collectively and then the girls collectively?

How many square miles of territory did paraguay lose in the war

Nosotros no (asistir) a la clase ayer. asistirimos asistimos asistemos asistamos