From trigonometry we know this relationship:
[tex]sin\alpha = \frac{O}{H}[/tex]
Being:
O: Opposite side
H: Hypotenuse
From the problem, the trigonometric relationship is given by:
[tex]sin(35\°)= \frac{12}{c}[/tex]
Therefore:
[tex]O=12 \ and \ H=c[/tex]
Therefore this equation works for computing the hypotenuse of a right triangle. Thus:
[tex]H=c= \frac{12}{sin(35\°)}=20.92[/tex]