Answer:
19 inches
Step-by-step explanation:
You want the middle length of three odd integer lengths whose total is 57.
The middle length is the average of the three lengths, so is their total divided by 3:
middle length = (57 in)/3 = 19 in
The middle side length is 19 inches.
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Additional comment
The perimeter of the triangle is the sum of the lengths of its sides.
If you like, you can write an equation using x for the middle length. Then the other two are x-2 and x+2 and their sum is ...
(x-2) +(x) +(x+2) = 3x = 57
x = 57/3 = 19, as above
