A store buys a batch of slippers, and the price of each pair is 15% higher than the purchase price. If they sell all of them, they can make a profit of 120 yuan. If they only buy 80 pairs, the difference of 64 yuan is enough to cover the cost. How much is the purchase price of each pair of slippers?
某商店购进一批拖鞋，每双的售价比进价高15%，如果全部卖出，则可获利120元，如果只买80双，则差64元才够成本．每双拖鞋的进价是多少元？
<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>