Let X be the number and (X + 6) be the next multiple of 6. We write: (X)(X + 6) = 216 --> X^2 + 6X - 216 = 0 --> X = -18 and 12. Substituting the values, we have: X = 12 and X + 6 = 18, if X = -18, then X + 6 = -12. So the answers would be: (-18 and -12) and (12 and 18).
