You started out nicely
Then you rather wandered off.
This is tantalizingly familiar.
It's Algebra I from here. Don't forget the ORIGINAL Domain.
It appeared to be a more interesting problem if these were logs base 10, so I assumed that they were and just threw that step in without discussion to see if you were paying attention. You were! Good work.
log(100x) = log(100) + log(x)
After that, why would I say just "100"? We're stuck with the logarithm function until it is treated properly.