Answer:
In the attachment
Step-by-step explanation:
First, we list out the constraints we have, which are the numbers 16 and 21.
With these constraints, we can test out the different cases of the middle sum (as seen on the right), if one of the middle sums is equal to the numbers, we ignore that combination, and move on to the next, after finding the correct combination, we do testing and logical predictions and find the correct value.
