For the same product, the purchase price of store A is 10% cheaper than that of store B. Store A makes a profit of 20% of the purchase price, and store B sets the price at a profit of 15%. As a result, store A is 8.4 yuan cheaper than store B. What is the purchase price of store B? Yuan?
同一种商品，甲店比乙店进价便宜10%，甲店按进价20%的利润，乙店按15%的利润定价，结果甲店比乙店便宜8.4元，乙店进价是多少元？
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) * (1/10)</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">(1/50) - 1 - (1/5)</gadget>
<output>-59/50 = around -1.18</output>

<gadget id="calculator">1 + (3/20) + (1/10) + (-59/50)</gadget>
<output>7/100 = around 0.07</output>

<gadget id="calculator">8.4 / (7/100)</gadget>
<output>120</output>

<result>120</result>