What are the three steps a CPU performs?
Three steps is probably minimal, and not really sufficient to describe the processing a CPU performs. If you have to use 3, probably fetch (the instruction), execute (the instruction) and store (write the results). However, this skips fetching the operands (if any). Most instructions require one or more operands.
If you assume the instruction is already fetched, you might classify the three steps as fetch the operand(s) (read them from memory), execute the instruction (perform an operation on the operands) and store (write the results to memory).
I think you will find it is more fetch, decode and execute are the three steps a CPU performs