"answers vary" is correct and usable in written English. You can use it when there is more than one answer to a given question or situation. For example, "What is the best way to teach a child to read? Answers vary depending on the child's learning style.".
Answers vary.
The answers vary.
The answers vary from region to region, and often from cook to cook.
When she asks neighborhood imams why they choose the newer, incongruous structures, the answers vary.
The answers varied.
Answers varied from "a few million" to "$25m tops".
But for years when people asked me where in Ireland, my answers varied.
Ludwig does not simply clarify my doubts with English writing, it enlightens my writing with new possibilities
Simone Ivan Conte
Software Engineer at Adobe, UK