Perimeter = (20 + 2x) mm.
Step-by-step explanation:
The octopus pupil has length 20 mm and the expression for its area is given by (20x - 200) square mm.
If the width of the octopus pupil is w, then 20w = 20x - 200
⇒ w = (x - 10) mm.
Therefore, the expression for its perimeter is 2(Length + Width) = 2 ( 20 + x - 10) = 2( 10 + x) = (20 + 2x) mm. (Answer)