There are 50 people in the examination room where I am taking the exam now, and there are 30 boys. How many girls account for the number of people in the examination room?
我现在考试的这个考场一共有50人，男生有30人，女生占这个考场人数的多少．
<gadget id="calculator">50 - 30</gadget>
<output>20</output>

<gadget id="calculator">20 / 50</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>