(PEMDAS)
First, you would start with parentheses, which is (31-9). This would equal 22.
(22-12÷2)
After that, you would do the division, which is 12÷2. This would equal 6.
(22-6)
Finally, you subtract 6 from 22, and this would equal 16.
Therefore, your final answer should be 16.
hope this helped! =^.^=