2024 DMC Mock 10 Problems/Problem 11

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First we use complementary counting to count the total number of possibilities. There are $4! = 24$ ways to arrange the officers without restrictions, and $2 \cdot 6! = 12$ ways if the treasurer and president sit next to each other, so the officers can sit in a total of $24 − 12 = 12$ (Error compiling LaTeX. Unknown error_msg) ways. Similarly, there are $4$ ways for both the treasurer and vice president to sit next to the president. Therefore, the answer is $\frac{12-4}{12}=\boxed{\frac{2}{3}}$.