Factor $448=8^{2}\times 7$. Rewrite the square root of the product $\sqrt{8^{2}\times 7}$ as the product of square roots $\sqrt{8^{2}}\sqrt{7}$. Take the square root of $8^{2}$.
$$6\times \frac{8\sqrt{7}}{6}$$
Divide $8\sqrt{7}$ by $6$ to get $\frac{4}{3}\sqrt{7}$.
$$6\times \frac{4}{3}\sqrt{7}$$
Express $6\times \frac{4}{3}$ as a single fraction.
