Using triangle inequality (let a, b, c be the side lengths of a triangle. a+b>c, and vice versa). The least length of the third side is 4 because 3+4>6. This is not possible for 3 because 3+3 is not greater than 6. The greatest is 8 because 3+6>8. It cannot be 9 because 3+6 is not greater than 9.
