Frank,
I would explain this [the house edge when betting pass and don't pass simultaneously] more intuitively in that betting pass and don't pass doesn't zero out the house advantage because of the boxcars.
Betting pass and don't pass doesn't protect you in the come out roll if a 12 is rolled. Assuming that you are at a $5 table, you will have $10 bet. When the 12 is rolled, on average one time out of 36, you will lose $5. The pass/don't pass bet has a house advantage then of ($5/(10 x 36)) 1.389%.
Some people might try to get around this by putting a buck on the 12. In which case, you win $25 when the 12 is rolled, but you lose $1 the other 35 times. Over 36 come-out rolls, on average then, you will lose $10 instead of $5 which ups the house advantage to ($10/(11 x 36)) 2.525%. No matter what combination of pass/don't pass you use, putting money on the 12 will always increase the house advantage (HA). The more you put the 12, the more the HA increases.
Thanks,
Tim
Thank you, Tim. Your response was well written and gives good information.
