A piece of iron sheet is 4 square meters, if you cut off (3/5) of this sheet of iron sheet for the first time, and cut off (1/4) of this sheet of iron sheet for the second time, what fraction of this sheet of iron sheet is left?
一张铁皮4平方米，第一次剪去这块铁皮的(3/5)，第二次剪去这块铁皮的(1/4)，还剩这块铁皮的几分之几？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (3/5) - (1/4)</gadget>
<output>3/20 = around 0.15</output>

<result>3/20 = around 0.15</result>