oookkkkk:
how many possible different oblivion gate spawn locations are there?
Without looking at the wiki:
90 random spawn locations
Plus some fixed ones: One for each city, except the Imperial City (8). Plus the great gate and associated minor gates. And the gate at Fort Such.
Max of 60 gates you can close yourself. (EDIT: Because not all 90 possible locations get a gate).
Plus some misc gates, like the two Daedric Shrines and minor gates before the Great Gate, but you don't close them -- at least not directly.
EDIT: So the answer you're looking for is probably 90+10=100.
Noticed TestedPrawns guessed 100, I'm just gave more detail. So if Mr. Spartan III says 100 is the answer, TestedPrawns should get the green thing I think.