Answer:
36 ft²
Explanation:
equilateral means all sides are equally long.
a triangle has 3 sides.
in our case they are all equally long.
and their sum (all 3 sides together) is the perimeter
P = 18 = 3 × side length
side length = 18/3 = 6 ft
a square with the same side length (6) had then an area of
side length × side length = 6×6 = 6² = 36 ft²
it is important to remember : a length is measured e.g. in feet (ft). an area is then meshed in square-feet (ft²). it is important to add this to the calculated numbers to express the right dimension of these numbers.