Chapter 4 - Writing Linear Functions - 4.6 - Arithmetic Sequences - Exercises - Page 214: 14

$-60,-90$ and $-120$.

Each term is $30$ less than the previous term. So, the common difference is $-30$. Add $-30$ to a term to find the next term. The next three terms are $-30+(-30), -30+2(-30)$ and $-30+3(-30)$. That is, $-60,-90$ and $-120$.