Question 205723
A  rough  sketch  shows  this  to  be  a  right  triangle,  with  legs, 14 &21, seeking  the  hypotenuse.
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Pythagorous ,  c^2 = a^2 +b^2,  applies
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c^2 = 14^2 +21^2 = 196 + 441 =637
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c=25.24 ft