Answer:
They will both inspect every 180 cartons.
Explanation:
Firstly you could find the LCM of 20 and 36.
Multiples of 20 are: 20, 40, 60, 80, 100, 120, 140, 180, etc...
Multiples of 36 are: 36, 72, 108, 144, 180, 216, 252, 288, etc...
Therefore 180 is the answer, all they were asking was what was the LCM. Hope this helped you !!