C(-10,2) D(-7,6)





Draw in these two green lines and you have a right triangle



Now you can count the number of units in the two green lines,
which are the two legs of the right triangle and the hypotenuse
of the right triangle is the distance between the two points.

The bottom side of the triangle is 3 units in length.
The right side of the triangle is 4 units in length.

So we use the Pythagorean theorem:













So the line CD is 5 units long

Edwin