Based on this range answer of play top 70% against 100% it got me thinking.
Pre your opponent will open or call 3x with any hand.
Your choice is to open 3x, call 3x, or fold.
Clearly you can play top 50% and be ahead or tied with his range.
Since you have a blind to forfeit it seems like you would play more than top 50%. And would probably vary in SB or BB.
Can assume it gets checked down after that. Or you can make other assumptions but please state them.
I am not sure if I have the math correct.
sb 1 bb 2
3x = 6
The pot starts with 3 of blind dead money. But since you know your opponent will always open or call 6 that is dead money (I think). So the dead money is the 6 of the opponent plus your blind.
So from the sb I have to open / call 5 to win 7. That is 1.4 : 1 and should play top 58%. Which is like 33+, A2s+, K2s+, Q2s+, J2s+, T4s+, 95s+, 85s+, 75s+, 65s, 54s, A2o+, K3o+, Q5o+, J7o+, T7o+, 97o+, 87o.
So from the bb I have to open / call 4 to win 8. That is 2.0 : 1 and should play top 67%. Which is like 22+, A2s+, K2s+, Q2s+, J2s+, T2s+, 94s+, 84s+, 74s+, 64s+, 54s, A2o+, K2o+, Q4o+, J6o+, T6o+, 96o+, 86o+, 76o.
An error here is taking top x % of hands when it should really be equity versus random hand. SB down to 5/T unsuited and BB down to 3/5 unsuited so pretty close.
Because of the dead money you should play a pretty good share of hands you expect to lose.
