Hassan thinks his goldfish got chickenpox. He lost 70% of his collection of goldfish. If he has 60 survivors, how many did he have originally?

So the complete amount of fishes were 100%

70% died and 60 are left ...

so 100% - 70% = 60

100% - 70% = 30%

30% = 60 fishes ...

so 10% = 20 fishes

If you complete that percentage to 100

10% = 20, 100% 200