Answer:
65.8
Explanation:
The Law of Sines can be used to find side values from angles when a side and its opposite angle are given.
__
The relation is ...
a/sin(A) = b/sin(B)
Solving for 'a' gives ...
a = b·sin(A)/sin(B) = 100·sin(18°)/sin(28°)
a ≈ 65.8