When Li Gong typed a manuscript, he had already typed (2/5) of the manuscript, and after another 20 pages, half of the manuscript was typed. How many pages does this manuscript have?
李工打一份稿件，已经打了这份稿件的(2/5)，再打20页就打完了这份稿件的一半．这份稿件一共多少页？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(1/2) - (2/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">20 / (1/10)</gadget>
<output>200</output>

<result>200</result>