A pile of coal is removed for the first time (1/3), and the second time (2/5), there are still 120 tons left. How many tons are there in this pile of coal?
一堆煤，第一次运走(1/3)，第二次运走(2/5)，还剩120吨，这堆煤共有多少吨？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

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

<gadget id="calculator">1 - (1/3) - (2/5)</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">120 / (4/15)</gadget>
<output>450</output>

<result>450</result>