Every time we increas x by 1, we also increase y by 9. This means that the slope is 9:
[tex]m = \dfrac{\Delta y}{\Delta x} = \dfrac{9}{1} = 9[/tex]
When you know the slope [tex]m[/tex] of a line and one of its points [tex](x_0,y_0)[/tex], you can write the equation of the line using the formula
[tex]y-y_0=m(x-x_0)[/tex]
In your case, if for example we use the first point, we have
[tex]y-7=9(x-1) \iff y=9x-9+7 \iff y=9x-2[/tex]
