No they didn't choose arbitrarily, no one is supposed to always multiply before divide. It is mentioned in the article or whatever that there are different variations of the pnemonic device that people use, such as PEMDAS, BODMAS, etc. Notice how the M and the D switch places? That's because in the case of multiplication and division, its supposed to go from left to right. 9 is right

CAPTCHA
This question is for testing whether you are a human visitor and to prevent automated spam submissions.