The set is $$\{ x \in Q:x^2 =64/25 \} $$
I thought the answer was $\{ \frac{8}{5}, -\frac{8}{5} \}$ but I am told there are in fact 4 distinct elements:
$$\{ \frac{8}{5}, \frac{8}{-5}, \frac{-8}{5}, \frac{-8}{-5}, \}$$
So are there 2 elements in the set or 4?