Let's find y
[tex]\\ \sf\longmapsto m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]
[tex]\\ \sf\longmapsto \dfrac{-1}{7}=\dfrac{y-2}{3-1}[/tex]
[tex]\\ \sf\longmapsto \dfrac{-1}{7}=\dfrac{y-2}{2}[/tex]
[tex]\\ \sf\longmapsto -2=7y-14[/tex]
[tex]\\ \sf\longmapsto 7y=12[/tex]
[tex]\\ \sf\longmapsto y=12/7[/tex]
