A rope is (8/9) meters long, (1/4) is used up for the first time, and (3/10) is used up for the second time, what fraction of the rope is left?
一根绳子长(8/9)米，第一次用去它的(1/4)，第二次用去它的(3/10)，还剩这根绳子的几分之几？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (1/4) - (3/10)</gadget>
<output>9/20 = around 0.45</output>

<result>9/20 = around 0.45</result>