Determine whether this statement is true or false?

Ø ∈ { Ø, {Ø} }

is true, plainly, because the set

{ Ø, {Ø} }

is described in roster notation, listing its elements,

and the list includes Ø.

[The other listed member of that set, {Ø},

is the set containing Ø (the null set) as its only element,

and therefore it is not empty and is not equal to Ø.

This may be a little bit of a stretch, if you're not used to the distinction,

but it doesn't matter to the answer to the question. Ø is a listed element

of the set, and therefore a statement which says its an element is just as true

as if the case we were considering was

2 ∈ {2,3}

]