There are some math problems, calculation problems are 4 times as much as application problems, Xiaoyun does 10 calculation problems and 3 application problems every day, after a few days, there are 20 calculation problems left, all application problems are done, how many of these math problems are there road?
有一些数学题，计算题是应用题的4倍，小云每天做10道计算题和3道应用题，若干天后，计算题还剩下20道，应用题全部做完，这些数学题共有多少道？
<gadget id="calculator">20 / 10</gadget>
<output>2</output>

<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">(2/5) - (1/3)</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">2 / (1/15)</gadget>
<output>30</output>

<gadget id="calculator">5 * 30</gadget>
<output>150</output>

<result>150</result>