The answer is ten. 6+4(half of eight)=10
It's all in the words.
Ten had no "eye"
9 had no tail
6 had no head
Half of eight is 4
So what it's saying is that each fish was missing an eye, 9 had no tail, 6 of them had no head. And the other 4 had no eye and tail but had a head.
55 Gallon Cichlid build in the works