Deductions from the Given Information

Because $O$ is the center of the circle, we can see that $OR$ and $OS$ are both radii of the circle. That of course means that $\angle R$ and $\angle S$ are equivalent (see diagram below).

From this, we can make another deduction. We know that the three angles of a triangle sum to $180$ degrees, giving us this equation below:

$$60 + x + x =180$$

Solving the equation, we see that $x$ is equal to $60$ and triangle $ROS$ is equilateral. The given information tells us that the perimeter of $ROS$ is $6$, so we can conclude the radius is $2$ (see diagram below).

Solving the Problem

Quantity A is the circumference of the circle, which can now be found since we deduced the radius ($r=2$) from the given information.

$$2 \pi r = 4\pi = \approx 12.56$$

In comparison with Quantity B, $12$, we can clearly see that Quantity A is larger.