u use the slope formula
slope = (y2 - y1) / (x2 - x1)
and u label each set of points :
set 1 : (2,-6)...x1 = 2 and y1 = -6
set 2 : (-3,-4)...x2 = -3 and y2 = -4
now u sub...pay attention to ur signs
slope = (-4 - (-6) / (-3 - 2) = (-4 + 6) / -5 = 2/-5 = -2/5