原式=12ab^2(a^4b^4c^4)÷(-3a^2b^3c)÷(2a^3b^3c^3)
=12÷(-3)÷2*a^(1+4-2-3)b^(2+4-3-3)c^(4-1-3)
=-2a^0b^0c^0
=-2