The area of the polygon = Sum of area of eight triangles + area of a square.
Area of the square
[tex]\begin{gathered} \\ \text{Length = 14cm} \\ \text{Area of the square = Length}^2 \\ \text{ = 14}^2 \\ =196cm^2 \end{gathered}[/tex]Area of one triangle
[tex]\begin{gathered} =\text{ }\frac{Base\text{ x Height}}{2} \\ \text{Base = 4cm} \\ \text{Height = 7cm} \\ =\text{ }\frac{4\text{ x 7}}{2} \\ =\text{ }\frac{28}{2} \\ =14cm^2 \end{gathered}[/tex][tex]\begin{gathered} \text{Area of the eight triangles = 8 x 14 } \\ \text{ = 112 cm}^2 \end{gathered}[/tex][tex]\begin{gathered} \text{Area of the polygon = 196 + 112} \\ \text{ = 308 cm}^2 \end{gathered}[/tex]