The two points are (x1,y1) = (3,-1) and (x2,y2) = (5,-8)
Plug those coordinates into the slope formula below.
m = (y2-y1)/(x2-x1)
m = (-8 - (-1))/(5 - 3)
m = (-8 + 1)/(5 - 3)
m = -7/2
Answer: The slope is -7/2
note: the fraction -7/2 converts to the decimal form -3.5
