Concept:
The output of an LTI system is obtained using convolution:
\[
y[n]=x[n]*h[n].
\]
First simplify the input sequence.
Step 1: Determine the values of \(x[n]\).
\[
x[n]=-u[n]+2u[n-3]-u[n-6].
\]
Hence,
\[
x[n]=
\begin{cases}
0,& n \\
-1,& 0\le n \\
1,& 3\le n \\
0,& n\ge6
\end{cases}
\]
Step 2: Determine the values of \(h[n]\).
\[
h[n]=u[n+1]-u[n-10].
\]
Thus
\[
h[n]=1,\qquad -1\le n\le 9.
\]
Step 3: Evaluate convolution in the interval \(5\le n\le9\).
Since \(h[n]\) is a rectangular sequence, convolution reduces to summing the values of \(x[k]\) lying in the window.
For \(5\le n\le9\),
\[
y[n]
=
-(3)+(6-n)
\]
which simplifies to
\[
y[n]
=
n-9.
\]
Step 4: Write the final answer.
\[
\boxed{y[n]=n-9}
\]