What is the sum of two consecutive even numbers, the difference of whose squares is 84?

Answer: Option C

Explanation:

Let the numbers be x and x + 2.

Then, (x + 2)^{2} - x^{2} = 84

4x + 4 = 84

4x = 80

x = 20.

The required sum = x + (x + 2) = 2x + 2 = 42.