Answer
Non-invertible
Work Step by Step
The matrix is non-invertible if and only if $D=0$.
Upper A$=\begin{bmatrix}
1 & 2 &-3&5\\
0 & 4 &-6 &11\\
0 & 0 &\frac{7}{2} &-\frac{13}{4}\\
0 & 0 & 0& 0
\end{bmatrix}$
Hence here $D=1.4.\frac{7}{2}.0=0$, thus the matrix is non-invertible.
