Answer
The figure name is a square. The perimeter is $72$ mm and the area is $324$ mm$^{2}$
Work Step by Step
1. State the figures name:
Square, since all sides have equal lengths.
2. Find the perimeter of the square
Let $P = $ the perimeter of the square
$P = 4(18)$
$P = 72$ mm
3. Find the area of the square
Let $A = $ the area of the square
$A = 18 \times 18$
$A = 324$ mm$^{2}$
