In a right triangle, the ratio of the opposite side of one angle to the hypotenuse is called sine.
In this problem the side JK is the opposite side of angle JLK whose value is 63 degrees. The hypotenuse is JL whose value is 8.
So the sine ratio of angle JLK would be
sin L=JK/JL
Substituting the numerical values,
sin 63°=JK/8
This implies JK=sin 63°×8 from wich we will get the value of JK
So, this equation sin 63°=JK/8 will let us solve for jk and the answer is the third one.