There are (2/3) liters in a barrel of gasoline. The first time I used (1/5) liters, the second time I used more (2/15) liters than the first time. How many liters of gasoline are left in this barrel?
一桶汽油有(2/3)升．第一次用了(1/5)升，第二次比第一次多用(2/15)升．这桶汽油还有多少升没用完？
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

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

<gadget id="calculator">2 / 15</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">(1/5) + (2/15) + (1/5)</gadget>
<output>8/15 = around 0.533333</output>

<gadget id="calculator">(2/3) - (8/15)</gadget>
<output>2/15 = around 0.133333</output>

<result>2/15 = around 0.133333</result>