急求一个英文请假条，高分报答！！！

Dear Sir or Madam,
I feel so sorry to tell you that I would like to know if I could ask for a casual leave of absence for three hours,for some family matters happened urgently and I have to go back home to solve them.As for the work I may miss,I will make up for it later on,please set your heart at rest.I will appreciate for your understanding.
Yours sincerely
***

供楼主参考，不知道字数够不够。

Dear Miss Gao,

I'm sorry I have to go home right now for a moment. My neighbour just called me that my grandma didn't feel well at home. So I should go back home to look after her. If necessary, I will take her to hospital to see a doctor and take some medicine. Now I am writing to you to ask for 3 hours. Thanks for your kind understanding.
With best wishes
Your students,
Tom

通过“有道词典”就可以了，中文翻译成英文，英文翻译中文都很容易，完全可以自己写，而不用请人。