The ratio of girls to the whole class is 5:7, and there are 15 fewer boys than girls, so how many people are there in the class?
女生与全班人数比是5：7，男生比女生少15人，那么全班有多少人．
<gadget id="calculator">5 / 7</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">1 - (5/7)</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">(5/7) - (2/7)</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">15 / (3/7)</gadget>
<output>35</output>

<result>35</result>