I do to the second exercise, since the first one is incomplete:
- Oigo algo ↝ No oigo nada
- Leo la novela ↝ No leo la novela

In this case, to create negative sentences, a "no" is mostly placed before the verb. Although depending on the tense it may or may not vary.
As the indefinite pronoun of the first sentence "algo" (something) is to refer to a thing in a positive way, to change it to negative it must be changed to "nada" (nothing).