Answer:
The Yankees lost <em>20%</em> of their games.
Step-by-step explanation:
We need to find the percentage of what games the Yankees lost.
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We need to figure out what percentage of 64 is part of 80 (the <em>winning </em>percentage) first.
We would have to divide 64 by 80 and the multiply the quotient by 100.

<em>The Yankees won 80% of the games. </em>
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To find the <em><u>losing percentage</u></em> we have to subtract 80% from the 100% of the games.
100% - 80% = 20%
<em>The Yankees lost 20% of the games.</em>
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Hope this helps!