Answer
$\left\{
12,10.5,9,7.5,6
\right\}
$
Work Step by Step
With $a_1=12$ and $d=-1.5$, then,
\begin{array}{l}
a_2=a_1+d\\
a_2=12+(-1.5)\\
a_2=10.5
,\\\\
a_3=a_2+d\\
a_3=10.5+(-1.5)\\
a_3=9
,\\\\
a_4=a_3+d\\
a_4=9+(-1.5)\\
a_4=7.5
,\\\\
a_5=a_4+d\\
a_5=7.5+(-1.5)\\
a_5=6
\end{array}
Hence, the first five terms are $
\left\{
12,10.5,9,7.5,6
\right\}
.$