Sorry for the stupid but brief question. With 3 total players and a 30 dollar pot when I am on the button with A10 on a J36 board, how do I figure the math here?
MP bets pot ($30) and it is called by the Cutoff. Am I calling 30 to get at 90 or do I think of it as calling 30 to get at 120? Don't think I ever understood that well. Thank you for your time.

You are investing $30 (1 unit) to win $90 or (3 units) and therefore you are getting 3:1.
If you put in the $30, then the pot becomes $120 of which $30 or 25% is yours. Your equity in the pot, moneywise is 25% or you "own" 25% of the pot once you call and 0% of the pot once you fold.

If you convert 3:1 to a percentage, your opponents put in 3 units to your 1 unit, and therefore 1/4th is yours which is 25% and now matches the previous calculation.

Assuming you have 9 outs to make the nuts with the flush (and discounting pair outs to the Ace), you have ~18% equity to bink it on the turn and ~36% equity to bink it by the river.

thank you for the excellent analysis. I really appreciate it.

That's a good analysis except for the wording where you say you "own 25%" of the pot. You dont own anything.

RottPhiler summed it up well. I'll just put it in other words.

You either think in ratios, in which case it is 30:90, which reduces to 1:3, aka 3-to-1 odds, or you think in percentages. If you use percentages, you put your call into the pot and then divide, which tells you what percentage of the pot you call represents. 30/120=.25, so your call represents 25% of the pot. Therefore you should only call if you have 25% or greater equity.

Remember that if you use percentages, you are dividing by the what would be the total pot with your call, so you add your call in there. If you are using odds, you do not. Percentage is percentage of the pot. Odds are ratio of price to potential winnings.

Pick one system and stick with it, so that you don't get confused. I prefer to use percentages, because that's what equity comes in, so I don't have to convert between the two systems.

Don't forget to account for IO as well ! especially w / NFD's

you simply add the amount that you expect to win the times you hit ( if im wrong plz correct me )

tricky part is figuring out how much you can expect to make when the front door flush comes in

Well that starts to explain my confusion. Great comment! really appreciate it.