Answer:
B: 50 feet
Explanation:
Let A represents the location of the swing, B represents the location of bench and C represents the position of slide,
According to the question,
AB = 100 ft,
BC = 80 ft,
m∠ABC = 30°,
By the cosine law,





Hence, the approximately distance between the swing and the slide is 50 ft.
Option 'B' is correct.