There were 200 fishes in an aquarium, 99% of which were red. how many red fishes must be removed to make the percentage of red fishes 98%?

If 200 fish are in the aquarium and 2 are non-red and 198 are red (99%), to not increase the non-red fish count and remove red fish to achieve 98% red fish in the aquarium, one would have to remove 100 red fish from the aquarium.

the new 100 fish in the aquarium would be 2 non-red fish with 98 (98%) red fish

... answer, ... remove 100 red fish.