kind of leather shoes in a shoe store are going to be sold at a preferential price. If they are sold at 80% of the original price, each pair will still make a profit of 4.2 yuan. If they are sold at 60% of the original price, each pair will lose 0.6 yuan. What is the cost of each pair of these leather shoes?
鞋店的一种皮鞋准备以优惠价出售，如果按原售价的80%出售，每双仍获利4.2元，如果按原售价的60%出售，每双要亏本0.6元．这种皮鞋每双的成本是多少元．
<gadget id="calculator">4.2 + 0.6</gadget>
<output>4.8</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(4/5) - (3/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">4.8 / (1/5)</gadget>
<output>24</output>

<gadget id="calculator">24 * (4/5)</gadget>
<output>96/5 = around 19.2</output>

<gadget id="calculator">(96/5) - 4.2</gadget>
<output>15</output>

<result>15</result>