Greetings from Brasil...
Here we cant use calculator..... It seems that in the USA the use of a scientific calculator is allowed
Let's use Senos Law in Any Triangle
(AC/SEN B) = (BC/SEN A)
16/SEN 39 = BC/SEN 120 sen 120 = sen 60 = √3/2
16/0,63 = BC/(√3/2)
0,63BC = 16√3/2
BC = 8√3/0,63
BC ≈ 22