The store brought in a batch of towels, sold them (2/5), and brought in 720 more. At this time, there were more towels than before (1/2). How many towels were originally brought in?
商店运进一批毛巾，卖了(2/5)，又运进720条，这时毛巾比原来多了(1/2)，原来运进毛巾多少条？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) - 1</gadget>
<output>-1/2 = around -0.5</output>

<gadget id="calculator">(2/5) + 1 + (-1/2)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">720 / (9/10)</gadget>
<output>800</output>

<result>800</result>