First represent your 3 consecutive integers as follows.
X ⇒ first integer
X + 1 ⇒ second integer
X + 2 ⇒ third integer
Since their sum is 84, our equation reads x + (x + 1) + (x + 2) = 84.
Simplifying on the left side we get 3x + 3 = 84.
Now subtract 3 from both sides to get 3x = 81.
Dividing both sides by 3, we find that x = 27.
Finally, make sure you list all your answers.
If x is 27 then x + 1 is 28 and x + 2 is 29.