My question is: in which way this exercise should be solved? It can't be solved with F test, because there were no given F-test value table on the exam, so it has to be another way to solve it. The only thing I can formulate are hypotheis:

H0: μ1 = μ2 = μ3

H1: at least one mean is different.

How exercise looks:

Investigating 3 types of fishes in the lake. Biologists claim, that their populations are equal. There were cathed 30 fishes by random, first type - 15, second - 8, third 7. Does this sample compatible with biologists guess with alpha=0.1.

Thank you.