Explanation:
I'm going to assume you mean 
 which can be rewritten as
 which can be rewritten as 
 since if you start with
 since if you start with 
 since when you do (10^x)^c you're just multiplying the exponent which is represented by the x but is equal to the log you just multiply the log which is why you can bring it in front.
since when you do (10^x)^c you're just multiplying the exponent which is represented by the x but is equal to the log you just multiply the log which is why you can bring it in front. 
You can then approximate the value of log(5) using a calculator and multiply by 125 to get around 87.371