We can divide the hexagon into 6 equilateral triangles, and call the side 'x'. I will draw the situation:
Every line is x because the hexagon is regular (all sides have the same length). Therefore we can find x, because two times x is 18'':
[tex]2x\text{ = 18}[/tex][tex]x\text{ = 9 inches}[/tex]
The hexagon has the same area of 6 equilateral triangles with the side equal to x. The formula of the area of an equilateral triangle is:
[tex]Area\text{ = }\frac{x^2\sqrt[]{3}}{4}[/tex]
Therefore the area of the hexagon will be:
[tex]\text{AreaHexagon = 6}\times\frac{x^2\sqrt[]{3}}{4}^{}[/tex][tex]\text{AreaHexagon = 6}\times\frac{9^2\sqrt[]{3}}{4}^{}[/tex][tex]\text{AreaHexagon }\cong210.44\text{ square inches}[/tex]
Rounding it will be 210 square inches.
