To find leg $ a $ use formula:
$$ \tan \left( \alpha \right) = \dfrac{ a }{ b } $$After substituting $ \alpha = 10^o $ and $ b = 75 $ we have:
$$ \tan( 10^o ) = \dfrac{ a }{ 75 } $$ $$ 0.1763 = \dfrac{ a }{ 75 } $$$$ a = 0.1763 \cdot 75 $$$$ a = 13.2245 $$