You should try using factoring the expressions :

7. Is p divisible by 168?
(1) p is divisible by 14
(2) p is divisible by 12

looking at the problem statement we realize that 168 is a multiple of 24.
if we factor it we get 168=7*24.
24 can be further written as 12*2 ->that can be written as (2^2*3)*2 = 2^3*3

thus 168 = 7* 2^3*3

now to divide out this entire length of primes we need the same primes in the denominator.



look at the statements

1>p/14 = I, thus we have 2*7 |2>p/12 = I, we got 2^2*3
i dont have any info about the rest factors | but we are still missing a 2 and a 7.

roping in statement 1 we get a 7. But overall we are still missing a 2.

note that we need to take LCM while considering both statements together. So the 2 in statement 1 is already counted while taking the 2-2's from statement 2. Dont make the mistake of adding the number of repetitive 2's and 3's from both the statements.

hence answer is E.

try applyin this to all the problems at hand.