From your other posts I assume you started with , and want to rearrange to make x the subject. By the way - to avoid confusion iit would have been better to add your attempt to your previous thread rather than start a new one - that way we wouldn't have to guess at what the original problem was.
So far so good
No - if you divide both sides by 3 the right hand side becomes . This is not the right approach. Instead from the previous expression you can gather the x terms:
Now divide both sides by and you're done.