When a product is sold at a 20% discount, the selling price is 64 yuan, so the profit rate is 28%, so how much is the purchase price of this product?
一种商品打八折出售时售价为64元，所利润率为28%，那么这种商品的进价是多少元？
<gadget id="calculator">28 / 100</gadget>
<output>7/25 = around 0.28</output>

<gadget id="calculator">1 + (7/25)</gadget>
<output>32/25 = around 1.28</output>

<gadget id="calculator">64 / (32/25)</gadget>
<output>50</output>

<result>50</result>