Answer:
y ≈ 60.6 units
Explanation:
Given a triangle with angles 18° and 117°, and sides 21 opposite 18° and y opposite 117°, you want to know the value of y.
Law of sines
The law of sines tells you the ratios of side length to the sine of the opposite angle are the same for all side/angle pairs in the triangle.
y/sin(117°) = 21/sin(18°)
y = 21·sin(117°)/sin(18°) ≈ 60.55
The value of y is about 60.6 units.