Source: http://examples.gurobi.com/traveling-salesman-problem
I don't get this part: (look at the source)
$$\sum_{i,j\in\{1,2,3\},i\neq j} x_{ij}=3>2=|\{1,2,3\}|-1$$
I get that $x_{ij}$ is equal to 3, but why the "> 2" ?
And what is the deal with subtracting 1 from a set? How do you even do that?
How come $|\{1,2,3\}|-1 = 3 > 2$ ?!?
Okay so: $$|\{1,2,3\}|-1 = 2$$
So how is he allowed to write: $$|\{1,2,3\}|-1 = 3 > 2$$
?
That is basically the same as writing: (which is incorrect right?) $$2 = 3 > 2$$
I don't get this part at all, please elaborate on what happened in as simple language as possible. My level is high school final math level.