The formula for determining slope is expressed as
Slope = (y2 - y1)/(x2 - x1)
Where
y2 and y1 are final and initial coordinates of y on the vertical axis
x2 and x1 are final and initial coordinates of x on the horizontal axis
From the information given,
x1 = 12, y1 = 2
x2 = - 7, y2 = 5
Slope = (5 - 2)/(- 7 - 12) = 3/- 21
Slope = - 1/7