m=8 is the slope
(2,-7) is a point on the line
y = mx + b is the equation
Steps:
(1) fill in what you know
y=8x + b
(2) plug in the coordinate
-7=8(2)+b
(3) solve for b
-7 = 16 + b
-16 -16
-----------------
-23 = b
(4) plug in what you found out
y = 8x - 23
That would be your answer.
Hope I helped!!
~A