Given that => a < 150 and b < 25
Classes have a maximum of 15 students

Target question => Can the ''a'' students be distributed among the b teachers so that the class has the same number of students?

Statement 1 => It is possible to divide the students evenly into groups of 2, 3, 5, 6, 9, 10 or 15
Number of students = LCM of 2,3,5,6,9,10 and 15 = 90 Since b < 25
If b = 15, then students can be evenly distributed 90/15 = 6 but if b = 24, then students cannot be distributed evenly.
Since the exact value of b is unknown. Statement 1 is NOT SUFFICIENT

Statement 2 => The greatest common factor of a and b is 10
This doesn't give us the exact value of a and b and there are more than 1 combination of 2 numbers with 10 as their HCF. So, we cannot ascertain if the student can be evenly distributed because of the variation in a and b. Statement 2 is NOT SUFFICIENT

Combining both statements together =>
None of the statements give the exact value of b so we cannot determine if students can be evenly distributed.
Both statements together ARE NOT SUFFICIENT

Answer = E