[AaronBrown]

The missing piece of information is that the bet is $3,600 to you. So if you go all-in, you call $3,600 and raise $5,600. If he calls your $5,600 raise, there is $7,200 + $9,200 + $5,600 = $22,000 in the pot.

If he does not call, you win the $7,200 in the pot.

If he does call, you win $22,000 - $9,200 with probability 0.22 and lose $9,200 with probability 0.78. Since you lose the $9,200 either way, you can write this as 0.22*$22,000 - $9,200.

Therefore, your overall expectation is 7200x + (1-x){(.22)(22000) - 9200} = 0 as you wrote. Note that you might have put in some of the $7,200 in the pot at the beginning (in heads up play, you will have put up $3,600 of it), but this is left out of the calculation. Once the money's in the pot, it doesn't matter who put it there.