1. The problem statement, all variables and given/known data The question says: Find the number of X-M-X angles in MX6, which has an octahedral geometry. 2. Relevant equations None 3. The attempt at a solution To do this question , I used p&c . Since there are 6 X in MX6 and we have to choose two of them . Therefore total number of M-X-M bonds will be 6C2=15. But the solution says that it is 12. When I saw it , I noticed that they had missed the opposite M-X-M bonds. So why had they(the solution makers) not counted those bonds? Are they wrong here ?