9 + 12 / 2 x 2

Question

I'm faced with adding parentheses to find the solution. However, the solution that I came up with was incorrect. Using PEMDAS, I placed the parentheses around 2 x 2, making the equation: 9 + 12 / 4. After that, I solved 12 / 4, getting 3, final answer being 9 + 3 = 12. When I compared my answer to the correct answer, the solution ended up being 21, as the author placed parentheses around 12 / 2, multiplied that by 2, and added 9. Which is truly correct?

Answer 1

MD stands for multiply or divide. Neither has priority. In such a case, proceed from left to right. 

So here you would do 12/2 before dealing with the multiplying by 2.

 

Then you do  get 9 + 6x2 = 21.