We have:\(\left\{{}\begin{matrix}a+2b=11\\a-b=-4\end{matrix}\right.\)\(\Rightarrow\left(a+2b\right)-\left(a-b\right)=11-\left(-4\right)\Rightarrow3b=15\Rightarrow b=5\)

\(\Rightarrow a=b-4=5-4=1\)\(\Rightarrow4a-b=4.1-5=-1\)

a-b=-4

\(\Rightarrow\)2a-2b=-8

\(\Rightarrow\)a+2b+2a-2b=11-8

\(\Rightarrow\)3a=3

\(\Rightarrow\)a=1

\(\Rightarrow\)b=a+4=1+4=5

\(\Rightarrow\)4a-b=1.4-5=4-5=-1

We have:{a+2b=11a−b=−4⇒(a+2b)−(a−b)=11−(−4)⇒3b=15⇒b=5

⇒a=b−4=5−4=1

⇒4a−b=4.1−5=−1