[tex]\displaystyle\\
a)~~\left(\frac{1}{4}x^6 \right)\cdot (8x^2)=\frac{x^6\cdot8x^2 }{4}=\frac{\cdot 8x^{6+2} }{4}=\boxed{2x^8}\\\\\\
b)~~(9x^3)\cdot \left(\frac{4}{3}x^3 \right)=\frac{9x^3\cdot 4\cdot x^3}{3}=\frac{36x^{3+3}}{3}=\boxed{12x^6}
[/tex]
