I haven't seen a formula or method, and I am not familiar with permutations or combinations.

Was this exercise given to you in some math course? It's not really fair for students, when schools assign problems dealing with topics not covered in class!

You need to study some lessons, before trying to understand how to count arrangements.

Try googling keywords

permutations with repetition, and look for written lessons or videos that you can understand. Work through the given examples, step by step, using paper and pencil. Make sure you understand the steps, before moving on. Once you have some idea about what you're supposed to be doing, try your exercise again. If you get stuck, you can then come back here and show us what you tried or explain

*why* you're stuck. If you see something in a lesson or example that you don't understand, let us know.

If the topic of counting permutations with repetition seems too confusing, then back up and start your search for lessons on

basic counting principles and

difference between combinations and permutations. If you cannot locate any lessons that help, please chat up your instructor.

This forum is not an on-line classroom. We provide tutoring. In general, the volunteers here don't have time to type up lectures about general topics or to duplicate lessons that already exist in many forms and locations on the Internet. :cool: