$4+4-1=7$ 
Ben and Ken have some books. After Ben sends $4$ books to Ken, he has $1$ fewer book than Ken. Which of the following is true? 

a: Originally, Ben had $3$ more books than Ken. 
b: Originally, Ben had $4$ more books than Ken. 
c: Originally, Ben had $1$ fewer book than Ken. 
d: Originally, Ben had $9$ more books than Ken. 
e: Originally, Ben had $7$ more books than Ken. 