$241-42+36=235$ 
Alex had some trading cards. After giving $36$ trading cards to Ben, Alex received another $42$ trading cards from David. If Alex has $241$ trading cards now, how many trading cards does he have at first? 
[a] $$235$$ 
[b] $$230$$ 
[c] $$225$$ 
[d] $$220$$ 