What number 21# I’ll mark brainliest

Evaluate the following expression 1/3^2

This is about circle theorems. someone asap : (

The area of a rectangle is 10 cm^2. one side of the rectangle is x cm. express the perimeter of the rectangle in terms of x and show that this rectangle cannot have a perimeter of 12 cm. the perimeter of the rectangle in terms of x is __ cm