By what percent will a fraction change if its numerator decreases by 85% and the denominator decreased by 25%

Let x/y be the original fraction.

After decreasing the numerator by 50% and decreasing the denominator by 25%, the fraction is:

(x - 0.5x) / (y - 0.25y) = (0.5x) / (0.75y)

 = (2/3)(x/y) = 66 2/3% of x/y

So, the fraction decreased by 33 1/3%.  

The correct answer is 80%

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