Dear Jimmy,
Thank you for inviting me to go to the movie,but I am too busy to go with you.I will visit my grandpa and grandma with my father and mother on Saturday morning and I will help my father wash the car on Saturday afternoon.On Sunday morning I need help my mother do housework and go shopping with her.I must be pepared for the English test that afternoon.And I will attend the birthday party of my father's friend that evening.So I'm sorry I can't accept your invitation.
Yours sincerely,
Ann