To find area $ A $ use formula:
$$ A = a \cdot h $$After substituting $ a = \frac{ 18 }{ 5 } $ and $ h = \frac{ 18 }{ 5 } $ we have:
$$ A = \frac{ 18 }{ 5 } \cdot \frac{ 18 }{ 5 } $$$$ A = \frac{ 18 }{ 5 } \cdot \frac{ 18 }{ 5 } $$$$ A = \frac{ 324 }{ 25 } $$