10 years ago, the age of the mother was 6 times that of the daughter, and 10 years later, the age of the mother was twice that of the daughter. How old is the daughter this year?
10年前母亲的年龄是女儿的6倍，10年后母亲的年龄是女儿的2倍，今年女儿多少岁．
<gadget id="calculator">2 * 20</gadget>
<output>40</output>

<gadget id="calculator">40 - 20</gadget>
<output>20</output>

<gadget id="calculator">6 - 2</gadget>
<output>4</output>

<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">5 + 10</gadget>
<output>15</output>

<result>15</result>