To find area $ A $ use formula:
$$ A = a \cdot b $$After substituting $a = 9\, \text{cm}$ and $b = \dfrac{ 40 }{ 3 }\, \text{cm}$ we have:
$$ A = 9\, \text{cm} \cdot \frac{ 40 }{ 3 }\, \text{cm} $$$$ A = 9\, \text{cm} \cdot \frac{ 40 }{ 3 }\, \text{cm} $$$$ A = 120\, \text{cm}^2 $$