The school transported (7/8) tons of yellow sand, used (1/3) to build the wall, and used (2/5) to build the playground. What fraction of this pile of yellow sand is left?
学校运来(7/8)吨黄沙，砌墙用去(1/3)，建操场用去(2/5)，还剩这堆黄沙的几分之几？
<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>

<result>4/15 = around 0.266667</result>