The answer would be ten.
The Pythagorean theorem is a squared plus b squared equals c.
c would equal the hypotenuse.
b is the opposite.
a is the adjacent.
you would do 24 squared plus x squared = 26 squared
after you square 24 and 26
576+x=676
-576. -576
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x=100
square root it to get
x=10
d is your answer