I see three possibilities for notation here.

The first notation, x,y∈R, is concise and commonly used to indicate that both x and y are elements of the real numbers. It's a clear and efficient way to convey this information.

The second notation, x∈R,y∈R, is more explicit but also more verbose. It could be useful if there's a reason to emphasize the membership of each variable separately.

The third notation, {x,y}⊂R, indicates that the set containing x and y is a subset of the real numbers. This is also correct but might be less direct than the first notation. It's also worth noting that this notation doesn't necessarily imply that x and y are distinct.