Lets first find how often you make the nut low and lets say your hand is A 2 3 9.


P(two low cards w/no A 2 3)= 4C2 (16)/45C2


P(two low cards w/exactly one A 2 3)=


9(16)/45C2


P(making nut low= 96 +144/ 45C2


=240/990.


So a naiver answer would be 12/99 or 87 to 12.

But you may get quartered and you often have to pay another bet on the turn.


SO if you only have to pay a bet on the flop, if you make the nut low you win half, and you don't get anything if you don't make the nut low draw the 87-12 figure is correct.