The term "hypotenuse" suggests this triangle is a right triangle. Then the other leg can be found using the Pythagorean theorem:
x^2 +12^2 = 24^2
x^2 = 576 -144 = 432
x = √432 ≈ 20.8 . . . cm
The other leg is about 20.8 cm.
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<em>Additional comment</em>
A right triangle with a short leg that is 1/2 the length of the hypotenuse is the "special" 30°-60°-90° right triangle. The longer leg is √3 times the length of the short leg: 12√3 ≈ 20.8 cm.
