x and y are positive integers. When x is divided by 17, the remainder is 3, and when x is divided by 19, the remainder is 1. When y is divided by 14, the remainder is 5, and when y is divided by 21, the remainder is 12. What is the least possible value of y - x?	Choose the correct choice from the following.
A) 15 B) 13 C) 11 D) 14 E) 18

Rationale: when x is divided by 17 , the remainder is 3 : so , the possible values of x are : 3 , 20 , 37,54 , etc . when x is divided by 19 , the remainder is 1 : so , the possible values of x are : 1,20 . . . stop . since both lists include 20 , the smallest possible value of x is 20 . when y is divided by 14 , the remainder is 5 : so , the possible values of y are : 5 , 19 , 33,47 etc . when y is divided by 21 , the remainder is 12 : so , the possible values of y are : 12 , 33 , . . . stop . since both lists include 33 , the smallest possible value of y is 33 since the smallest possible values of x and y are 20 and 33 respectively , the smallest possible value of y - x is 13 . so , b is the correct answer to the original question .
Answer: B