What is the rule of 1/6, 1/2, 5/6,___,1 1/2 and whats the missing number?

Suppose a triangle has two sides of length 32 and 35, and that the angle between these two sides is 120°. which equation should you solve to find the length of the third side of the triangle?

What percent of the circle below is shaded?

How is working backward similar to solving an equation?