The price of a stereo is increased by 2/5 due to the improved functions, and the current price is 5600 yuan. How much is the original price of this stereo? (Solution of column equation)
一台音响，由于改进了功能，每台提价(2/5)，现在售价是5600元，这台音响原价多少元？(列方程解)
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 + (2/5)</gadget>
<output>7/5 = around 1.4</output>

<gadget id="calculator">5_600 / (7/5)</gadget>
<output>4_000</output>

<result>4_000</result>