题目内容：

Dear Mr. Smith，Thank you for your kind letter inviting me go and       51.______

stay several days with you. But I'm terrible sorry to say        52.______

that I can't go this summer vacation， for I promised           53.______

to go and spend the holidays with my grandma， who live in the countryside. 54._______

I'd like to tell you that I get on well with my study.          55.______

And I must own the success in my English for your              56.______

help. At present I'm busy all day prepare for the              57.______

examinations and I feel sure I'll success.                     58.______

I do hope we can meet with each other soon.                    59.______

With best regard to you and Tom.                               60.______

Sincerely yours Jack