Let:
[tex]\begin{gathered} (x1,y1)=(0,2) \\ (x2,y2)=(2,0) \\ \text{The slope is:} \\ m=\frac{y2-y1}{x2-x1}=\frac{0-2}{2-0}=\frac{-2}{2}=-1 \end{gathered}[/tex]Using the point-slope equation:
[tex]\begin{gathered} y-y1=m(x-x1) \\ y-2=-1(x-0) \\ y-2=-x \\ y=-x+2 \end{gathered}[/tex]