Xiao Ming bought 3 story books, paid 30 yuan, and got back a yuan. How much is each story book.
小明买3本故事书，付30元，找回a元．每本故事书多少元．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">10 - (1/3)</gadget>
<output>29/3 = around 9.666667</output>

<result>29/3 = around 9.666667</result>