Olá, Wellington.
a) [tex]\begin{cases}2x-y+6=0\\2x+3y-6=0\end{cases}\Rightarrow\begin{cases}2x-y=-6\\2x+3y=6\end{cases}\Rightarrow\begin{cases}x^*=-\frac{3}{2}\\y^*=3\end{cases}[/tex]
b) [tex]\begin{cases}x+y-2=0\\3x-y+4=0\end{cases}\Rightarrow\begin{cases}x+y=2\\3x-y=-4\end{cases}\Rightarrow\begin{cases}x^*=-\frac{1}{2}\\y^*=\frac{5}{2}\end{cases}[/tex]
c) [tex]\begin{cases}x-2y=0\\x+y-1=0\end{cases}\Rightarrow\begin{cases}x-2y=0\\x+y=1\end{cases}\Rightarrow\begin{cases}x^*=\frac{2}{3}\\y^*=\frac{1}{3}\end{cases}[/tex]