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24. If x and y are integers between 10 and 99, inclusive, is (x-y)/9 an integer?
(1) x and y have the same two digits, but in reverse order.
(2) The tensâ€™ digit of x is 2 more than the units digit, and the tens digit of y is 2 less than the units digit.
From the stem we can see that 0=<(x-y)=<89
From 1 we get:
AB-BA = a multiple of 9 for (x-y)/9 to be an integer. Plugging in any numbers relevant to the stem for this starting with x=1 and y=1, and its clear that the difference between AB-BA is a multiple of 9. SUFF
2) doesn't give us enough. Say x could be 42 and y could be 24, this would be suff. But if x is 86 and y is 35 its insuff.