Explanation

Reducing a number by a percent involves multiplication; reducing a number by a fixed amount involves subtraction. The order of operations (PEMDAS) will make a difference.

One possible value for the item is $100. In this case, the value of Quantity A = ($100)(0.9) – $20 = $70. The value of Quantity B = ($100 – $10)(0.80) = $72. Here, Quantity B is greater.

However, a greater starting value may change the result, because a 20% discount off a greater starting value can result in a much greater decrease. For a $140 item, the value of Quantity A = ($140)(0.9) – $20 = $106. The value of Quantity B = ($140 – $10)(0.80) = $104.

Here, Quantity A is greater. The relationship cannot be determined from the information given.
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For this, I chose the extremes of $91 and $149. Not pretty, but makes me feel secure in my logic.

Starting with $91:
Quantity A: 10% pride reduction = $81.90, followed by $20 off, leaves you with $61.9
Quantity B: $10 off = $81, followed by 20% reduction, leaves you with $64.8
Quantity B is greater

Then, using $149:
Quantity A: 10% price reduction = $134.1, followed by $20 off leaves you with $114.10
Quantity B: $10 off = $139, followed by 20% reduction, leaving you with $112.20
Here, Quantity A is greater.

Since we have two different answers, we don't have enough information to come to a definitive conclusion. Answer is D.

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