Xiaoming did 12 math problems, which belonged to Xiao Hong (2/3), and the math problems done by Xiao Hong belonged to Xiao Gang (3/5). How many math problems did Xiao Gang do?
小明做了12道数学题，是小红的(2/3)，小红做的数学题又是小刚的(3/5)，小刚做多少道数学题？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">12 / (2/3) / (3/5)</gadget>
<output>30</output>

<result>30</result>