Correct option is C
Total time taken by B to complete the whole work = 4×4 = 16 days
We know, efficiency is inversely proportional to time
So, time ratio for A to B = 2 : 1
So, total time taken by A to complete the whole work = 16×2 = 32 days
Total work = 32 unit
3x + 2×4 = 32
3x = 24
x = 8