Answer:
[tex]\large\boxed{12\sqrt5}[/tex]
Step-by-step explanation:
[tex]\text{Use}\ \sqrt{ab}=\sqrt{a}\cdot\sqrt{b}\\-----------------\\\\-4\sqrt{15}\cdot\left(-\sqrt3\right)=4\sqrt{(15)(3)}=4\sqrt{5\cdot3\cdot3}=4\sqrt5\cdot\sqrt9\\\\=4\sqrt5\cdot3=12\sqrt5[/tex]
