To whet your appetite and keep your writing fingers limber, take a good look at the photo or let a prompt settle in your mind. Set a timer for some amount of time, be that five, fifteen, or thirty minutes, and start writing.
Tell the tale of a girl who is obsessed with numbers and is on a mission to make everyone like math as much as she does. Bonus points if pi figures prominently in your story.
Write about your experience with math when you were young. Did you enjoy it? Was it hard? What is your attitude toward math today and how was that shaped by your early experiences?
Write an article explaining what pi is and how it works.