Hi there! :)
Answer:

5n + 6 = -3n - 10
Solve for n:
Add 3n to both sides:
5n + 3n + 6 = -3n + 3n - 10
8n + 6 = -10
Subtract 6 from both sides:
8n + 6 - 6 = -10 - 6
8n = -16
Divide both sides by 8:
8n/8 = -16/8
n = -2.
x^2 - 81 = 0. Add 81 to each side.
x^2 = 81. Take the square root of each side.
x = 9, -9
x = 16 x sin(60) = 8sqrt(3)
answer is B.