Say you invest $50 (in stocks, staking a poker player, hiring a prostitue to re-pimp out) and you get $150 back. Your ROI (Return On Investment) is 200% which is your original inventment plus double back.

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If you feel you have a question, dont be lazy; make sure you have asked yourself first. Then search the forum, then just fucking google it to get as much detail as you can. You may then seek clarification on specific points from others.