To find side $ a $ use formula:
$$ A = \dfrac{ \sqrt{ 3 } \cdot a^2 }{ 4 }$$After substituting $A = 6.93\, \text{cm}$ we have:
$$ 6.93\, \text{cm} = \dfrac{ \sqrt{ 3 } \cdot a^2 }{ 4 }$$ $$ 6.93\, \text{cm} \cdot 4 = \sqrt{ 3 } \cdot a^2 $$ $$ 27.72\, \text{cm} = \sqrt{ 3 } \cdot a^2 $$ $$ a^2 = \dfrac{ 27.72\, \text{cm} }{ \sqrt{ 3 } } $$ $$ a^2 = 16.0041\, \text{cm} $$ $$ a = \sqrt{ 16.0041\, \text{cm} } $$$$ a \approx 4.0005 $$