For the point 13. we have that the line passes through the points (-1,-2) and (0,1) then the slope is
and the line equation will be:
For the point 14: we have that the line passes through the points (-1,0) and (0,-1) then the sslope is:
and the line equation will be:
For the point 15: the line equation is y=-3 because the y coordinate will be always the same (-3) and the slope of the line will be equal to zero