#### Answer

0.7124

#### Work Step by Step

If $a\gt0$, $a\ne1$, $b\ne1$, and $x\gt0$, then we know that $log_{a}x=\frac{log_{b}x}{log_{b}a}$.
Therefore, $log_{7}4=\frac{log_{10}4}{log_{10}7}\approx\frac{0.6021}{0.8451}\approx0.7124$.
Recall that $b$ can be any positive number other than 1.