Each of X1, X2 and X3 represents a nonzero digit of the 3-digit base M positive integer X1X2X3; where X1, X2 and X3 are not necessarily distinct.
Determine the possible positive integer values of M, with 7 ≤ M ≤ 206, such that this equation has at least one valid solution.
X1X2 + X2X3 + X3X1 = X1X2X3 ± 6
Note: X1X2X3 denotes the concatenation of the three digits.