Aaron has a saltwater aquarium. He likes to keep the ratio of fish to crabs at 5 : 2 as shown in the tape diagram. If Aaron has a total of 21 sea creatures in his aquarium, how many of each type of creature does he have in the tank? Use the tape diagram to support your answer.

In Space 1: Write the number of FISH he has.
In Space 2: Write the number of CRABS he has.
In Space 3: What NUMBER did you put in each box of your tape diagram to find your answers?