You sold two complimentary tickets for a variety entertainment. But at the end of the day you found for whom you purchased an additional ticket he/she is not going to join you. Alone you will get bore, in this case it is better if any of your friend will join you. So to request a friend you need to drop an email. Find the Format below.
Sample Letter to invite your Friend
My dear <Your Friends Nickname>,
Many thanks for your kind letter of 31st July. I am very sorry it has taken me long to send this reply. The day I received your letter I left for Trichur to play in the State Football Tournament. I hope you will excuse me for my long silence.
On my return from Trichur, I find two complimentary tickets for a Variety Entertainment waiting for me. The show is coming off on Sunday next and is being organized by the local Youth Club. I shall be most happy it you can come with me to the show.
Some of the city recreation clubs, and music and dance sabhas are presenting very interesting items and the show is bound to be entertaining. The highlight of the show, I am told, is a scene from Kathakali presented by the Kerala Club. I know how interested you are in this art form and I hope you will find it convenient to come. Please drop me a line in reply.
My regards to your parents.
<Your Full Name>