help please

 

James is playing an arcade game with tokens. In the firstgame, he hits the jackpot and doubles the number of tokens that he has. In the second game, James wins 12 more tokens. In his third and final game, he loses 4 tokens. James now has 170 tokens. How many tokens did he have before he started playing the game?     

 

Let "x" stand for the original amount      

 

                           2x + 12 – 4  =  170      

 

                           2x  =  170 – 12 + 4     

 

                           2x  =  162     

 

                             x  =  81     

_.