/sci/ - Science & Math

Sup /sci/, I tried the appropriate board for this, I really did.... but /adv/ is fucking retarded and useless... anyways, here's my problem.

Hello, my mother got into trouble recently, and needs advice.

My mom owns a small jewelry (fake: beads, some crystals and shit) store here in Canada, Quebec.

here's the tl;dr:

>Mexican tries to sell stolen goods to my mom who works at a jewelry store
>asks for some payment in advance
>scams my mom and leaves
>next day, 2 mexican men try to enter the store while door is locked
>mom is freaked out and paranoid
what do?

I'll explain in detail in the next posts

How the fuck do I show that the difference between the empty set and a set A is the empty set?

Ø - A = Ø

What I got so far :

let x be in Ø - A
so x is in Ø and x is not in A
x is in Ø is false, so we have F and x not in A

but then im stuck, because then that whole statement is false and it doesn't take me anywhere