Answer:
las clases difíciles
Explanation:
Add an <em>-s</em> to <em>clase</em>, and add an <em>-es</em> to <em>difícil</em> because adjectives have to match the plurality of the word they describe.
there are several verbs that could be used here, but I would recommend gustar.
a mí me gusta el béisbol.
El Perro quere conocer el gato