B is the correct answer. To find out why it is, we can simply put 2,800, the whole, as 100% and 6.2 into x=6.2. The left sides of both of them have the same units, and both right sides have the same units, so we can do something such as 2800/x=100%/6.2%. Then, you simply solve for x.
STEPS:
2800/x=100/6.2
(2800/x)*x=(100/6.2)*x - we multiply both sides of the equation by x
2800=16.129032258065*x - we divide both sides of the equation by (16.129032258065) to get x
2800/16.129032258065=x
173.6=x
x=173.6
