Moving from (-3, -6) to (3, 2), x increases by 6. Draw a triangle and use this 6 as the length of the base. y increases by 8. Label the height of the triangle with this 8. Then find the hypotenuse (which is also the desired distance) by using the Pythagorean Theorem:
6^2 + 8^2 = d^2, where d is that distance:
36 + 64 = 100 = d^2, and so d = 10. The distance in question is 10 units.
