$$13-7=6$$ 
As a Grade 1 student, Jenny saw thirteen seats in a row in the class, and she didn\textquotesingle t know which one belonged to her. The teacher told her that there were seven students behind her seat. So which seat should she sit?(Adapted from 2015 Math Kangaroo Problem, Level 1-2, Question \#18)  ~\hspace{0pt}\hspace{0pt}\hspace{0pt}\hspace{0pt} 

  $$5$$\textsuperscript{th} 
  $$6$$\textsuperscript{th} 
  $$7$$\textsuperscript{th} 
  $$8$$\textsuperscript{th} 
  $$9$$\textsuperscript{th} 