Hi Vincen,
We're told that the number "A" is a two-digit positive integer, the number "B" is a two-digit positive integer formed by REVERSING the digits of A and Q = (10B - A). We're asked for the value of Q. This question can be solved by TESTing VALUES...
1) The tens digit of A is 7
With the information in Fact 1, we can refer to the two integers as...
A = 7 _
B = _ 7
IF....
the missing digit is 1, then the A=71, B=17 and the answer to the question is 170 - 71 = 99
the missing digit is 2, then the A=72, B=27 and the answer to the question is 270 - 72 = 198
Fact 1 is INSUFFICIENT.
2) The tens digit of B is 6
With the information in Fact 2, we can refer to the two integers as...
A = _ 6
B = 6 _
IF....
the missing digit is 1, then the A=16, B=61 and the answer to the question is 610 - 16 = 594
the missing digit is 2, then the A=26, B=62 and the answer to the question is 620 - 26 = 594
the missing digit is 3, then the A=36, B=63 and the answer to the question is 630 - 36 = 594
This pattern repeats, regardless of what the missing digit is, so the answer to the question is ALWAYS 594
Fact 2 is SUFFICIENT.
Final Answer: B
GMAT assassins aren't born, they're made,
Rich
