There are 39 pens in a row. The red pen is 9th from the left end and the green pen is 21st from the left end. How many pens are there between red and green pen?

There are 39 pens in a row. The red pen is 9th from the left end and t

1.	There are 39 pens in a row. The red pen is 9th from the left end and the green pen is 21st from the left end. How many pens are there between red and green pen?
A.	11
B.	12
C.	10
D.	13
Answer» B. 12