"掷钱币决胜负" can be translated into English as "flip a coin to decide the winner/outcome" or "settle a matter by coin toss".
Here are some context-specific variations:
For a general decision-making scenario: "Let's flip a coin to decide."
For a competitive context (e.g., sports): "We'll determine the winner by a coin toss."
For a playful or casual tone: "How about a coin flip to settle this?"
The choice depends on the nuance you want to convey!