The slope=(difference between the y coords)/(difference between the x coords)=
(3-(-6))/(2-(-5))=(3+6)/(2+5)=9/7.
To find out which line passes through the points we take one point and use the coords:
for point A: y-3=(9/7)(x-2). So y=(9/7)(x-2)+3, y=9x/7-18/7+3, y=9x/7-18/7+21/7, y=9x/7+3/7.
This can be written 7y=9x+3 or y=(9x+3)/7. If you put x=-5 into this y=(-45+3)/7=-42/7=-6, and this is point B(-5,-6) so it looks like we got the equation of the line right!