broy wrote:The concentration of a certain chemical in a full water tank depends on the depth of the water. At a depth that is x feek below the top of the tank, the voncentration is 3 + (4 / sqrt(5 - x)) parts per million, where 0<x<4. To the nearest 0.1 foot, at what depth is the concentration equal to 6 parts per million?

a. 2.4 ft
b. 2.5 ft
c. 2.8 ft
d. 3.0 ft
e. 3.2 ft

The OA is 3.2 ft...but how?