To find side $ a $ use Pythagorean Theorem:
$$ h^2 + \frac{ a^2 }{ 4 } = s^2 $$After substituting $ h = 7.2 $ and $ s = 9.7 $ we have:
$$ 7.2^2 + \frac{ a^2 }{ 4 } = 9.7^2 $$ $$ \frac{ a^2 }{ 4 } = 9.7^2 - 7.2^2 $$ $$ \frac{ a^2 }{ 4 } = 94.09 - 51.84 $$ $$ a^2 = 42.25 \cdot 4 $$ $$ a^2 = 169 $$ $$ a = \sqrt{ 169 } $$$$ a = 13 $$