9514 1404 393
Answer:
5
Explanation:
The left side simplifies to ...
2x +16
The right side simplifies to ...
2x +21 -__
The x-terms are already equal. To make the constant terms equal, we want ...
16 = 21 -__
The blank must be filled with the value 21-16 = 5 to make the statement true.
5 goes in the blank.