The house advantage is what $1 minus what you would expect to have after $1 bet. The probability of winning this bet is 16/52 (16 tens out of 52 cards) =~ 30.8%. If you win you triple your money so you $1 bet on insurance on average will yield $3 * .308 = 92.3 cents. Thus the house advantage is 1.00 - .923 = 7.69%.

Let x be the number of non-tens you would have to remove to make this a fair bet. Since it pays 2:1 you should have a 1 in 3 chance of winning for it to be fair.

1/3 = 16/(52-x)
52-x = 48
x=4.

Thus you would have to remove four non-tens from a single deck game to make this a fair bet.

Michael Shackleford, A.S.A.