10 years ago, the age of the father was 7 times that of the daughter, and 15 years later, the age of the father was twice that of the daughter, so what is the age of the father now?
10年前父亲的年龄是女儿的7倍，15年后父亲的年龄是女儿的2倍，那么现在父亲的年龄是多少岁．
<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</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">30 - 15 - (20/7)</gadget>
<output>85/7 = around 12.142857</output>

<gadget id="calculator">20 + (85/7)</gadget>
<output>225/7 = around 32.142857</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">(225/7) / (5/7)</gadget>
<output>45</output>

<result>45</result>