well, your distance equation is right.
and to use the pythag. Theorm, you just draw a right triangle with those two points, and solve for the hypotenuse, because you have the 2 legs.
The line that connects the two points is the hypotenuse. Then just make a right triangle with that.
To find the midpoint, you take the average of the 2 x coordinates and the 2 y coordinates, and combine those 2 averages, to make 1 ordered pair.
So the X coordinate of the midpoint will be 1.55
So the Y coordinate of the midpoint will be 2
So the midpoint will be: