Hi M7MBA,

We're told that the students in a class are arranged to form groups of 4 members each and after forming the groups, 3 students are left. If the students had been arranged in groups of 9 members each, however, 4 students would be left. We're asked for the total number of students in the class. This question can be answered by TESTing VALUES and a bit of 'brute force' arithmetic.

To start, we can use the information we're given to list out some of the possibilities (the Facts mention 2-digit numbers, so we'll stick to just those):
-When we form groups of 4 members each, there 3 students are left. The total COULD be 11, 15, 19, 23, 27, 31, 35, 39, 43, 47, 51, 55, 59, 63, 67, 71, 75, 79, 83, 87, 91, 95, 99
-When we form groups of 9 members each, there 4 students are left. The total COULD be 13, 22, 31, 40, 49, 58, 67, 76, 85, 94
There are only 2 possibilities that are just 2-digits: 31 and 67

1) The number of students is a two-digit number less than 70.

With the information in Fact 1, we know that the total could be 31 or 67.
Fact 1 is INSUFFICIENT

2) The number of students is a two-digit number greater than 50.

With the information in Fact 2, we know that the total could only be 67.
Fact 2 is SUFFICIENT

Final Answer: B

GMAT assassins aren't born, they're made,
Rich