Equity × EQR ≥ required equity; if the left side is larger, continue, and if smaller, fold.
The core decision shared by every game; in standard terms: realized equity ≥ pot odds. Equity comes from your outs for a draw, or from your hand against the opponent's range preflop; EQR (equity realization) depends on position and hand shape; required equity depends only on the size of the opponent's bet. Example: with A4o in the CO against a UTG open, 38% equity is about the 38.5% needed, and after discounting for realization it falls short, so fold.