Liu Wei and Zhou Hong spent the same amount of money to buy the same number of exercise books. Later, Liu Wei took 13 books, Zhou Hong took 7 books, and Liu Wei gave Zhou Hong 1 yuan and 50 cents. How much is each exercise book.
刘伟、周红两人拿出同样多的钱买了同样多的练习本，后来刘伟拿了13本，周红拿了7本，刘伟给了周红1元5角钱，这种练习本每本多少钱．
<gadget id="calculator">5 / 10</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 + (1/2)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">13 - 7</gadget>
<output>6</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">(3/2) / 3</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>