I need to know what is the sequences?

a particular order in which related things follow each other.

77.38 (almost answer C)

Step-by-step explanation:

The area of the circle is πr² = 36π ≈ 113.097

The side length of the "other" right side of the triangle is √(12²-9²) = √63

The area of the triangle is (9√63)/2 ≈ 35.717

So the shaded area is the difference, ie.: 113.097-35.717 = 77.38