楼上都很好 这个是我套模板写的 仅供参考
Dear Wang ming,
I am excessively sorry to tell you that i can't go to the party this evening.
Now i am writing you this letter of apology to show my deep regret.
Please accept my sincere apology with gratitude.
Let me explain.The reason for my absence is that i have accepted another friend's invitation to the concert.
We may meet again and i hope to see you soon.
Sincerely yours
Wang xin