Tax law changes

Thank you so much for your response..... Please forgive me if I am trying to understand these tax implications with some added questions for my understanding going forward.... 
    Somewhere I read that ,,, half of total SS income is taxed ,,,, so in my case @ $1,673 X 12 = $20,076 / 2 = $10,038,,,, Is this not a starting place to determine taxes owed? 
     And,, then start  adding in additional income.... ?
Thanks again,,, Russ