a) \(\left(a\right)\left\{{}\begin{matrix}-2a+b=0\\0a+b=1\end{matrix}\right.\Rightarrow y=\dfrac{1}{2}x+1}\)
b) \(\left\{{}\begin{matrix}a+b=4\\3a+b=0\end{matrix}\right.\) \(\left\{{}\begin{matrix}a=-2\\b=6\end{matrix}\right.\) =>\(y=-2x+6\)
c) \(\left\{{}\begin{matrix}-2a+b=2\\a+b=5\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}a=1\\b=4\end{matrix}\right.\) => y=x+4