Given xy = 4y/x and x and y not 0.

Therefore you are able to divide both sides by 'y' such that:

x = 4/x

Multiply both sides by x:

x2 = 4 or x = +2 or –2.

Because of the fact that x could equal –2, the relationship cannot be determined from the information given.

In order to determine the relationship between Quantity A and Quantity B, let's convert both to square roots. In order to do this, we must square Quantity A so it becomes √81 which is equivalent to 9. Now to Quantity B, we must simplify by adding the two values together (25 + 55) to get √80.

√81 is greater than the √80 because 81 is greater than 80. Thus Quantity A is greater.

Since is between 10 and 20, it can be any real number between 100 and 400. Therefore, the relationship cannot be determined since could fall anywhere between these two limits, including between 399 and 400.