How do I calculate the reflection vector?

How do i calculate the reflection vector of this problem? I know from looking at it that the reflection vector is meant to be R(1, 0) but i dont understand how to get there. I have looked everywhere and every time this formula keeps coming up r = v−2(v⋅n)n. I have tried this and it doesnt give me the answer I'm looking for. Any help with this would be apprecenter image description hereiated and pls include the steps of to solve this?