sssaniaa Even I made the same mistake but the point to be noted is that EACH OF the team leader is managing P project managers and each of P project managers are managing D designers.
My approach :
It is quite clear that D has to be a multiple of 4, so with that we can eliminate a few numbers. Now let us assign a number for the Team Leaders. Starting with 3, if there 3 TL, then we would have 3*4 PM which is 12PM. If the number of Pm is 12, the the number of D will have to be a multiple of 12 and we clearly do not have a multiple of 12 in the options
Moving onto 4TL, we will have 16 PM and that means the number of D has to be a multiple of 16. 112 is the only multiple of 16, so the answer is 4 and 112 respectively
Hope this helps