To find side $ a $ use Law of Cosines:

$$ a^2 = b^2 + c^2 - 2 \cdot b \cdot c \cdot \cos( \alpha ) $$

After substituting $b = 9.3\, \text{cm}$, $c = 5\, \text{cm}$ and $\alpha = 112^o$ we have:

$$ a^2 = 9.3^2 + 5^2 - 2 \cdot 9.3 \cdot 5 \cdot \cos( 112^o ) $$ $$ a^2 = 86.49\, \text{cm}^2 + 25\, \text{cm}^2 - 2 \cdot 9.3 \cdot 5 \cdot \cos( 112^o ) $$ $$ a^2 = 111.49\, \text{cm}^2 - 2 \cdot 46.5\, \text{cm}^2 \cdot \cos( 112^o ) $$ $$ a^2 = 111.49\, \text{cm}^2 - 93\, \text{cm}^2 \cdot -0.3746 $$ $$ a^2 = 111.49\, \text{cm}^2 - -34.8384\, \text{cm}^2 $$ $$ a^2 = 146.3284\, \text{cm}^2 $$ $$ a = \sqrt{ 146.3284\, \text{cm}^2 } $$$$ a \approx 12.0966\, \text{cm} $$

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