If we take it as:
[tex]log (3x+4125)=3[/tex]
To solve this we have to understand the log this way:
[tex]log_{b} a=c <--> b^{c}=a[/tex]
and remember that when b is not shown it means it is 10. So:
[tex]10^{3} =3x+4125\\1000-4125=3x\\x=\frac{-3125}{3} =-1041.66[/tex]
