we know that
the Area of a circle=pi*r²
the length of a radius of circle circumscribed about an equilateral triangle is
r=b*(√3)/3
where
b---------> length of a side equilateral triangle-------> 18 in
then
r=18*(√3)/3=10.39 in
A=pi*(10.39)²=108*pi=339.29 in²
the answer is 339.29 in²