The question is asking you to find the measure of YZ's arc.
The arc of a circle is found by finding the central angle. In this case, that's angle YCZ. Remember that a circle's total degrees is 360. Since the angle that you are trying to find is 16% of the circle, you need to find 16% of 360.
360*0.16 = 57.6
The measure of arc YZ is 57.6 degrees.

As we have to solve for b, it means we have to isolate b
So first of all subtract
from both sides
So we get

Now we need b , but its b^2 , so we can take square root on both sides.
taking square roots on both sides

Hence option B is correct
She will need 12 seconds because -20•12=-240
(I'm not totally sure but there may be someone else with a more accurate/correct answer.)
Here is what I got (Red represents my work, blue represents to follow which steps and highlighter represents what the answer is):