Answer:
The third choice (the bottom one)
Explanation:
By law of sin, an angle over the side opposite of the angle is equal to another angle over side opposite of the angle. If that doesn't make sense, refer to the picture below. The first option is not applicable because y is not opposite the angle measuring 100 degrees. Therefore, law of sin cannot be applied. The second option is not applicable because y is not opposite the angle measuring 46 degrees. The third option is applicable because the side measuring 21 unites is opposite the angle measuring 46 degrees and side y is opposite the angle measuring 34 degrees.