Answer:
B. 28.5
Step-by-step explanation:
Before you can use the Law of Sines, you need to know the measure of angle C. The sum of angles in a triangle is 180°, so you have ...
A + B + C = 180°
C = 180° -A -B = 180° -32° -25° = 123°
The Law of Sines tells you ...
c/sin(C) = a/sin(A)
c = sin(C)·a/sin(A) = sin(123°)·18/sin(32°)
c ≈ 28.5
_____
Additional comment
The law of sines says the ratio of a side length to the sine of the opposite angle is a constant for any given triangle:
a/sin(A) = b/sin(B) = c/sin(C)
In order to use this relationship, you need to have a side length and its opposite angle. If you're solving for a side length, as here, you need to know the angle opposite that side.
This problem gives you side 'a' and angle A, and it asks for side 'c'. That means you need to know angle C, which we found as part of our solution.
