Xiao Ming has a pack of marbles, 25% of which are green, 10% are yellow, and the remaining 20% are blue. If there are 13 blue marbles, what is the number of marbles in this pack?
小明有一包弹球，其中25%是绿色的，10%是黄色的，余下的20%是蓝色的．如果蓝色的弹球是13个，那么这包弹球的个数是多少．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">13 / (1/5)</gadget>
<output>65</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/4) - (1/10)</gadget>
<output>13/20 = around 0.65</output>

<gadget id="calculator">65 / (13/20)</gadget>
<output>100</output>

<result>100</result>