1-with the numbers 1 and 2 we don't need to put the number because the noun and the number is one thing: ex: قرأت كتابا the word كتابا is singular ( means number 1 ) قرات كتابين the word كتابين is dual ( means number 2 ) 2- After numbers from 3 to 10 we need to put a plural with kasra ex : قرأت ثلاثة كتبٍ the word كتب is a plural because it comes after number 3 ( ثلاثة ) and you can replace ثلاثة with أربعة و خمسة .......... عشرة 3 - After numbers from 11 to 99 we need to put a singular with fat'ha ex : قرأت أحد عشر كتابًا and you can replace أحد عشر =11 with اثنا عشر - ثلاثة عشر ................. تسعة وتسعون =99