5teachers have fish tanks in their classroom. each teacher receives an equal number of tropical fish to put in his or her fish tank. each teacher also receives 6 goldfish. if there are between 34 and 56 fish in the school, how many tropical fish could there be?

There could be 5 tropical fish total. 
5 tropical + (6 goldfish * 5 teachers) = 35 fish

Or ten.
10 tropical + (6 goldfish * 5 teachers) = 40 fish 

Or twenty. 
20 tropical + (6 goldfish * 5 teachers) = 50 fish

I'm assuming that any of these is your answer so pick the one you like the best since it says COULD be the answer. Have a great day and I hope this helped!