Using cosine law.
b= sqrt(38^2 + 18^2 - 2(38)(18) Cos 36)
using calculator solve.
b = sqrt (1444 + 324 - 1106.75)
b = 25.75
Since these angles clearly form a circle and a circle is 360 degrees,
120-x+2x+16+3x-72=64+4x=360. Subtracting 64 from both sides, we get
4x=296 and by dividing both sides by 4 we get x=74
