find the slope if it exists of (-7,-3) and (-11,-19)

Are you looking for the slope of a line between said points?

If so, find the slope by dividing the difference in y by the difference in x.

(y-y0)/(x-x0), where (x0,y0) are the coordinates of the first point and (x,y) are the coordinates of the second.

Remember that a-(-b) = a+b