A barrel of gasoline, (1/4) barrel is used for the first time, (1/5) barrel is used for the second time, exactly 18 liters are used for the two times, how many liters are there in this barrel of gasoline?
一桶汽油，第一次用去(1/4)桶，第二次用去(1/5)桶，两次正好用去18升，这桶汽油共有多少升？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/4) + (1/5)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">18 / (9/20)</gadget>
<output>40</output>

<result>40</result>