The formula to find the slope of a line is m = [tex] \frac{y_2 - y_1}{x_2 - x_1} [/tex] where the x's and y's are your given coordinates and m is your slope. So, plug in your coordinates and solve.
m = [tex] \frac{y_2 - y_1}{x_2 - x_1} Plug in your coordinates
m = [tex] \frac{-2 - 7}{8 - -1} Cancel out the double negative
m = [tex] \frac{-2 - 7}{8 + 1} Simplify
m = [tex] \frac{-9}{9} Divide
m = -1
Now, plug that slope and one set of your given coordinates into point-slope form, [tex]y - y_1 = m(x - x_1)[/tex]. I'll use (-1, 7).
[tex]y - y_1 = m(x - x_1)[/tex] Plug in your points and slope
y - 7 = -1(x - -1) Cancel out the double negative
y - 7 = -1(x + 1) Use the Distributive Property
y - 7 = -x - 1 Add 7 to both sides
y = -x + 6