The distance d between two points with coordinates is given by .

This formula can be derived from the Pythagorean Theorem.

First draw a coordinate plane, plot the points X and Y.  

Form the right triangle using gridlines.

The measure of segment XY is the hypotenuse of the right triangle.

The Pythagorean theorem states that the square of the hypotenuse is the sum of

the squares of the legs. Let d ids the distance between points X and Y.

          (Substitute )

        (Take the square root each side)

From figure; coordinates of S and T are respectively.

Substitute the coordinate values in the midpoint formula.

                (Product of two same signs is positive)

                          (Add: 6 + 3 = 9)

                                   (Subtract: )

                                    (Evaluate power: )

                                          (Add: 81 + 9 = 90)

                                       (Use a calculator to find the value)

                                           (Round to the nearest tenth)

Distance between two points S and T is about 9.5 units.