其它
There are $20$ children lining up outside a theme park. John is the $14$\textsuperscript{th}~ person counting from the front of the line and Mary is the $2$\textsuperscript{th}~person counting from the back of the line. How many children are standing in line between John and Mary? 
Overseas Competition->Knowledge Point->Word Problem Modules
Mary is the $$20-2+1=19$$\textsuperscript{th} person in the line, so there are $$19-14-1=4$$ children are between them. 