So, if we put that alllll together.
(-3)(6)(m)(m)(m)(m)(m)(m)(m)(m)(m)(m)(m) = -18m11
When we multiply, we multiply the coefficients and add the exponents (with the same base).
Dividing is the opposite. We subtract the exponents (with the same base).
15m6/5m3 = 15(m)(m)(m)(m)(m)(m)/5(m)(m)(m)
15/5 = 3, and 3 of the m's cancel out, so we end up with 3m3.

David W.
Note: For any negative exponents (e.g., m^-4), be sure to change multiplication to division or else division to multiplication when you move values between numerator and denominator. For example: m^8 * m^3 = m^11 ... and m^6 / m^2 = m^6 * m^-2 = m^4.03/15/20