To find area $ A $ use formula:
$$ A = a \cdot b $$After substituting $a = 6\, \text{cm}$ and $b = \dfrac{ 9 }{ 2 }\, \text{cm}$ we have:
$$ A = 6\, \text{cm} \cdot \frac{ 9 }{ 2 }\, \text{cm} $$$$ A = 6\, \text{cm} \cdot \frac{ 9 }{ 2 }\, \text{cm} $$$$ A = 27\, \text{cm}^2 $$