The school cafeteria bought a cart of coal, burned (1/7) in the first month, and burned (2/7) in the second month, what fraction is left?
学校食堂买一车煤，第一个月烧了(1/7)，第二个月烧了(2/7)，还剩几分之几？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (1/7) - (2/7)</gadget>
<output>4/7 = around 0.571429</output>

<result>4/7 = around 0.571429</result>