https://larspsyll.wordpress.com/2022/12/29/combinatorics-vi/ Created Fri, 30/12/2022 - 01:21 Updated Fri, 30/12/2022 - 01:21 In my library, there are n philosophy books and six economics books. If yours truly can choose two books of each type in 150 ways, how many philosophy books are there in my library? Tags Statistics & Econometrics