You can put this solution on YOUR website!
For part a) you are looking for the midpoint. The midpoint between (a,b) and (c,d) is ((a+c)/2, (b+d)/2). So the midpoint between (12,6) and (8,2) is
((12+8)/2, (6+2)/2)=(20/2, 8/2) = (10, 4).
I will do b) also then you should be able to do the rest:
The distance between (a,b) and (c,d) is
So the distance between (6,4) and (18,4) is