Hope Primary School originally had 120 popular science books and literary books, among which popular science books accounted for (1/3). Later, some popular science books were bought, and at this time popular science books accounted for (3/5) of the two kinds of books. Then buy how many popular science books.
希望小学原有科普书、文艺书共120本，其中科普书占(1/3)，后来又买来一些科普书，这时科普书占两种图书的(3/5)．则又买进科普书多少本．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">120 * (1/3)</gadget>
<output>40</output>

<gadget id="calculator">120 - 40</gadget>
<output>80</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 - (3/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(3/5) / (2/5)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">80 * (3/2)</gadget>
<output>120</output>

<result>80</result>