How many different selections of four letters from the 12 letters of the word REFRIGERATOR contain no Rs and two Es?

Question

Leo Galleguillos · Answer

I would start by breaking this down. How many unique selections of four letters are there? How many contain no R's? How many contain exactly 2 E's?

Raj · Answer

Can I do it directly using 9/2! * 4!/4!

Raj · Answer

Let me know how you would do it?

bobpursley · Answer

https://math.stackexchange.com/questions/2872662/permutation-selection-of-4-letters-from-12