Mr. A is 5 years senior to Mr. B, Mr. B is 3 years senior to Mr. C, and Mr. C is 2 years junior to Mr. D in job experience . If Mr. D has 15 years job experience , how many years of experience does Mr. A possess ?

Correct Answer: 21
A = B + 5 = (C + 3) + 5 = {(D - 2) + 3} + 5 = 15 - 2 + 3 + 5 = 21.