You did fine to here.  Then you went astray. Now here is what 
you should have done:

Get your calculator at this point and calculate  as

.

and store it in the memory of your calculator, or write it down.
So you won't have to cary such a long awkward decimal through your
steps, just call it .  In other words let 


Now 

          

becomes simply

          

or switch the A to the left of the parentheses:

          

Distribute on the right:

          

Get all the x terms on the left and other terms on the right:

          

Factor out x on the left:

          

Divide both sides by 

          

Cancel the 's

          

          

Now using the recall feature of your calculator to substitute
the value of A.

          

Now calculate that with your calculator, and you'll get

          

Edwin