Structure, infrastructure, composition
Answer:
C. 9
Explanation:
Let's add up the other side of the equation first. So we do 9+11 according to the order of operations and we get 20. We then add 10 to 20 and we get 30. Now we look at the other side and see that the numbers are the same, except 11 and 9 will be flipped. So the blank is 9.
I hope this helped!
