14. For what value of $x$ is $64^{x}$ equal to $512^{5}$ ?
A 6
B 7.5
C 8
D 16
E 40
14. B Note that $64=2^{6}$ and $512=2^{9}$. Therefore $\left(2^{6}\right)^{x}=\left(2^{9}\right)^{5}$. So $2^{6 x}=2^{45}$. Hence $6 x=45$, that is $x=7.5$.