10 years ago, the age of the mother was 7 times that of the daughter, and 10 years later, the age of the mother was twice that of the daughter. What is the age of the mother now?
10年前母亲的年龄是女儿的7倍，10年后母亲的年龄是女儿的2倍．现在母亲的年龄是多少岁？
<gadget id="calculator">20 * 2</gadget>
<output>40</output>

<gadget id="calculator">10 / 7</gadget>
<output>10/7 = around 1.428571</output>

<gadget id="calculator">(10/7) * 2</gadget>
<output>20/7 = around 2.857143</output>

<gadget id="calculator">40 - 10 - (20/7)</gadget>
<output>190/7 = around 27.142857</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/7) * 2</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 - (2/7)</gadget>
<output>5/7 = around 0.714286</output>

<gadget id="calculator">(190/7) / (5/7)</gadget>
<output>38</output>

<result>38</result>