Factor out the largest term possible (Show work)

-18a^2 m^5 + 12a^4 m^3

Factor out the gcf for numerals

-6 (3a^2m^5-2a^4m^3)

Then factor out the largest common exponent for variable a

-6a^2 (3m^5-2a^2m^3)

Then factor out the largest common exponent for variable m

-6a^2m^3 (3m^2-2a^2)

Final answer: - 6a^2 m^3 (3m^2-2a^2)