#### Answer

$log_{7}200=y$

#### Work Step by Step

From the definition of the logarithmic function on page 456, we know that $b^{y}=x$ is equivalent to $y=log_{b}x$ (for $x\gt0$, $b\gt0$, and $b\ne1$).
Therefore, $7^{y}=200$ is equivalent to $log_{7}200=y$ in logarithmic form.