Answer: (-51 - x - z)/3
Step-by-step explanation: Let's call the three integers x, y, and z. We know that x + y + z = -51.
If we want to find the value of the middle integer, we can use the fact that the sum of the three integers is -51.
Rearranging the equation, we get: y = (-51 - x - z)/3.
So the value of the middle integer is (-51 - x - z)/3.