Answer
2.1004
Work Step by Step
For all positive numbers $a$, where $a\ne1$, and all positive numbers $x$, we know that $y=log_{a}x$ means the same as $x=a^{y}$.
Therefore, $log_{10}126=x$ means the same as $10^{x}=126$.
By using a calculator to approximate, we know that $x=2.1004$, because $10^{2.1004}=126$.