When the positive integer A is divided by 9 and 7, the remainder is 3 and 4, respectively. When the positive integer B is divided by 9 and 7, the remainder is 3 and 4, respectively. Which of the following must be a factor of A-B? Choose the correct choice from the following answers
A) 35	B) 48	C) 54	D) 63	E) 72
A = 9k+3 = 7j+4   B = 9m+3 = 7n+4   A-B = 9(k-m) = 7(j-n)   Thus A-B is a multiple of 9 and 7, so it is multiple of 63.   The answer is 63.
<result>D</result>
When the positive integer A is divided by 9 and 7, the remainder is 3 and 4, respectively. When the positive integer B is divided by 9 and 7, the remainder is 3 and 4, respectively. Which of the following must be a factor of A-B?