Chen Hong reads a book and reads it in three days. The number of pages read on the first and second days accounts for (2/5) of the total number of pages, and the number of pages read on the second and third days accounts for (9/10) of the total number of pages. ), what percentage of the total number of pages were read the next day?
陈红看一本书，三天看完，第一、二天看的页数占总页数的(2/5)，第二、三天看出的页数占总页数的(9/10)，第二天看的占总页数的几分之几？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">(9/10) - 1</gadget>
<output>-1/10 = around -0.1</output>

<gadget id="calculator">(2/5) + (-1/10)</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>