How? React Native is for cross-platform mobile applications while Rax only works in a web browser, as far as I can tell.
edit: Appears you're right, from the Rax tutorial [1]: "Rax is like React + React Native, you can use a component in the same way both in native and web as building blocks. " I guess this is possible because it's built on weex [2].
1: https://github.com/alibaba/rax/blob/master/docs/tutorial.md
2: https://weex-project.io/