Answer
$D=-40.683$
Work Step by Step
We know that for a matrix
\begin{bmatrix}
a & b & c\\
d & e &f\\
g & h & i
\end{bmatrix}
the determinant,
$D=a(ei-fh)−b(di−fg)+c(dh−eg)$
Hence here
$D=2.3(3.3\times5.7-5.1\times3.6)-1.5(4.2\times5.7-5.1\times6.8)+7.9(4.2\times3.6-3.3\times6.8)$
$D=2.3\times0.45-1.5\times(-10.47)+7.9\times(-7.32)$
$D=-40.683$
