Answer: 17/20
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Work Shown:
x% = x/100
85% = 85/100
85% = (17*5)/(20*5)
85% = 17/20
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You could also go through all the answer choices to see what works and what doesn't.
For instance, 4/5 = 0.80 = 80%, so that is a non-answer.
But 17/20 = 0.85 = 85% which is the answer.