[tex]y=-\cfrac{3}{7}x+3 \\\\[-0.35em] ~\dotfill[/tex]
[tex]A(x~~,~~\stackrel{y}{6})\qquad \qquad \begin{array}{llll} \stackrel{\textit{since we know that}}{y=-\cfrac{3}{7}x+3}\implies 6=-\cfrac{3}{7}x+3\implies 3=-\cfrac{3x}{7} \\\\\\ 21=-3x\implies \cfrac{21}{-3}=x\implies -7=x \end{array} \\\\[-0.35em] ~\dotfill\\\\ B(\stackrel{x}{9}~~,~~y)\qquad \qquad \begin{array}{llll} \stackrel{\textit{since we know that}}{y=-\cfrac{3}{7}x+3}\implies y=-\cfrac{3}{7}(9)+3\implies y=-\cfrac{27}{7}+3 \\\\\\ y=\cfrac{-27+21}{7}\implies y=-\cfrac{6}{7} \end{array}[/tex]
