A store buys a batch of slippers, and the selling price of each pair is 15% higher than the purchase price. If you sell all of them, you can make a profit of 120 yuan. If you only sell 80 pairs, the cost will be 64 yuan. How much is the purchase price of each pair of slippers?
某商店购进一批拖鞋，每双售出价比购进价多15%．如果全部卖出，则可以获利120元，如果只卖出80双，则差64元才够成本，问拖鞋每双的购进价是多少元？
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">120 / (3/20)</gadget>
<output>800</output>

<gadget id="calculator">800 - 64</gadget>
<output>736</output>

<gadget id="calculator">736 / 80</gadget>
<output>46/5 = around 9.2</output>

<gadget id="calculator">1 + (3/20)</gadget>
<output>23/20 = around 1.15</output>

<gadget id="calculator">(46/5) / (23/20)</gadget>
<output>8</output>

<result>8</result>