Hans bought 15 gold fish and 7 blue fish. To find out how many fish he bought in total, we need to add the number of gold fish and blue fish together. 

15 (gold fish) + 7 (blue fish) = 22 fish

Therefore, Hans bought a total of 22 fish.
Přidáme 15 k 7 a dostaneme 22. Takže Hans koupil 22 ryb v obchodě s domácími mazlíčky.