Q and R are two-digit positive integers that have the same digits but in reverse order. If the positive difference between Q and R is less than 20, what is the greatest possible value of Q minus R?	Choose the correct choice
A) 15  B) 16  C) 17  D) 18  E) 19
A two-digit integer "ab" can be expressed algebraically as 10a+b.   Q-R=(10a+b)-(10b+a)=9(a-b)&lt;20.   The greatest multiple of 9 which is less than 20 is 18.   The answer is 18.
<result>D</result>
Q and R are two-digit positive integers that have the same digits but in reverse order. If the positive difference between Q and R is less than 20, what is the greatest possible value of Q minus R?