Answer......

An integer is divisible by 3 if the sum of its digits is divisble by 3. An integer is divisible by 9 if the sum of its digits is divisible by 9. The sum of the digits in 957 is 21 (9+5+7=21), which is divisible by 3 but not by 9, so 957 is divisible by 3 but not by 9......

Dude, it took me forever and I still didn't understand it cuz I was trying to add up 1+0+9=10 and that is not divisible by either...and so on...until a friend of mine (Danny) explained how those other numbers are just there to throw me off..... =)

~GRE MATH PROBLEM from KAPLAN~