Glycolysis (cytoplasm, split glucose into 2 molecules)--> blank-->Blank--> ATP(usable energy)

Fill in the blank

The missing steps are:

1. Citric acid cycle (mitochondria, further breakdown of glucose)
2. Electron transport chain (mitochondria, production of ATP from electron carriers)

So the complete process is:
Glycolysis (cytoplasm) --> Citric acid cycle (mitochondria) --> Electron transport chain (mitochondria) --> ATP (usable energy)