[tex]\text{Use:}\\\\a^n\cdot a^m=a^{n+m}\\\\(-6a^5b^4c^3)(5a^3b^2c)\\\\=(-6\cdot5)(a^5a^3)(b^4b^2)(c^3c^1)\\\\=-30a^{5+3}b^{4+2}c^{3+1}\\\\=\boxed{-30a^8b^6c^4}[/tex]
