Answer: Choice B) $62.50
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Work Shown:
x = original price
20% = 20/100 = 0.20
20% of x = 0.20x = discount
x - 0.20x = 0.80x = final price
0.80x = 50
x = 50/0.80
x = 62.50
The original price of the jeans was $62.50
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Note how,
20% of x = 0.20*x = 0.20*62.50 = 12.50
Tara saves $12.50 (this is the discount).
The price she pays is x - 0.20x = 62.50 - 12.50 = 50 dollars, which matches with what your teacher gave in the instructions. This confirms we have the correct original price.