This question wants you to reverse the operations that occurred.
Start with 12 stamps.
Divide this number by 3/4. This represents Carla giving 1/4 of the stamps to Thomas.

Multiply this number by 2. This represents Jim giving half of the stamps to Carla.

Multiply this number by 2. This represents John giving half of his stamps to Jim.

John started out with
64 stamps.