When it's multiple choice, you can plug in each number until you find the correct answer. In this case: 9(-6)=3(-6)-36, which equals -54=-54. But, you can also solve for x without plugging in the numbers.
Theta = 210° r = 4.6/2 = 2.3 Area of circle = pi * r * r = 3.14 * 2.3 * 2.3 = 16.61 Area of sector = (theta / 360) * area of circle = (210/360) * 16.61 = 9.69