Mom buys a barrel of oil and uses about 1/10 of this barrel of oil every day. After a week, how much oil is left in this barrel
妈妈买回一桶油，每天约用这桶油的(1/10)，一周后，还剩下这桶油的多少
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(1/10) * 7</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 - (7/10)</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>