1)book($20$)-twenty books.
2)pen($17$)-seventeen pens.
3)pencil($19$)-nineteen pencils.
4)pencil case($15$)-fifteen pencil cases.
5)school bag($18$)-eighteen school bags.
6)ruler($13$)-thirteen rulers.
7)rubber($16$)-sixteen rubbers.
8)school($14$)-fourteen schools.
9)subject($12$)-twelve subjects.