we substitute y=-2x+17 in y=8-x

\(\displaystyle-{2}{x}+{17}={8}-{x}\)

\(\displaystyle-{x}=-{9}\)

\(\displaystyle{x}={9}\)

For x=9,y=8-9=-1

\(\displaystyle{x}={9},{y}=-{1}\)

\(\displaystyle-{2}{x}+{17}={8}-{x}\)

\(\displaystyle-{x}=-{9}\)

\(\displaystyle{x}={9}\)

For x=9,y=8-9=-1

\(\displaystyle{x}={9},{y}=-{1}\)