Answer
$-12x^{15}$
Work Step by Step
Based on the product rule for exponents, we know that $a^{m}\times a^{n}=a^{m+n}$ (where $m$ and $n$ are positive integers and $a$ is a real number).
Therefore, $(12x^{5})(-x^{6})(x^{4})=12\times-1\times x^{5+6+4}=-12\times x^{15}=-12x^{15}$.