You can put this solution on YOUR website! easiest way i remember to do it is to draw it on the graph, make your right triagle and use the pathagorean therom to solve for the hypotnuse.
so the sides in this case for a is 3 between -4 and -7 and b is 8 between 2 and -6.
a^2+b^2=c^2
a=3, b=8, find c 73 is prime this is the distance of the line between the 2 points, approx 8.544