Well first of all, 'kg' means mass, not weight.
If the total mass of all his baggage is 35 kg, and the mass
of his backpack is 4 kg, then the combined mass of all of his
checked bags is (35 - 4) = 31 kg.
If all of his checked bags have the same mass, then the mass
of each one is
(31 kg / 222 bags) = 139.64 grams/bag (rounded)
