Below is an instruction that describes a task. Write a response that appropriately completes the request in English. Please answer in English.

### Instruction:
Olga has an aquarium with fish in 5 different colors. There are 12 yellow ones, half as many blue ones, and twice as many green ones as yellow ones. How many fish does Olga have in her aquarium?

### Response:
The number of blue fish is 12 * 0.5 = <<12*0.5=6>>6.
The number of green fish is 12 * 2 = <<12*2=24>>24.
There are 12 + 6 + 24 = <<12+6+24=42>>42 fish in the aquarium.
#### 42