Question:
Solve for $a$: $\frac15|9+2a|<1$.  Express your answer in interval notation.

Answer:
Multiplying by 5 gives $|9+2a|<5$, so we must have  $$-5 < 9+2a < 5.$$Subtracting 9 from all three parts of this inequality chain gives  $$-14 < 2a < -4,$$and dividing by 2 gives $-7 < a < -2,$ or $a \in \boxed{(-7, -2)}$ in interval notation.