9.75 ft is the answer
[tex]By \: Pythagoras \: Theorem, \\ \boxed{ {hyotenuse}^{2} = {base}^{2} + {height}^{2} } \\ \\ here \\ hypotenuse = 12ft \\ base = 7 ft\\ height = x\ \\ \\ \ {12}^{2} = {7}^{2} + {x}^{2} \\ \implies144 = 49 + {x}^{2} \\ \implies {x}^{2} = 144 - 49 \\ =95 \\ x = \sqrt{95 } \\ = 9.75 ft\\ \\ \\ [/tex]
