Answer
$\text{Set Builder Notation: }
\left\{ t|t\lt-3 \right\}
\\\text{Interval Notation: }
\left( -\infty,-3 \right)$
Work Step by Step
Dividing both sides by a negative number (and consequently reversing the inequality symbol), then
\begin{array}{l}\require{cancel}
-5t\gt15
\\\\
t\lt\dfrac{15}{-5}
\\\\
t\lt-3
.\end{array}
Hence, the solution set is
\begin{array}{l}\require{cancel}
\text{Set Builder Notation: }
\left\{ t|t\lt-3 \right\}
\\\text{Interval Notation: }
\left( -\infty,-3 \right)
.\end{array}
In the graph, a hollowed dot is used for $\lt$ or $\gt.$ A solid dot is used for $\le$ or $\ge.$
