One year ago, the sum of the ages of the parents was 7 times the sum of the ages of the two brothers; 4 years later, the sum of the ages of the parents was four times the sum of the ages of the two brothers. It is known that the father is 2 years older than the mother. How old is the mother?
1年前，父母的年龄和是兄弟二人年龄和的7倍；4年后，父母的年龄和是兄弟二人年龄和的4倍，已知爸爸比妈妈大2岁，妈妈今年多少岁？
<gadget id="calculator">5 * 2 * 4</gadget>
<output>40</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">40 - 10</gadget>
<output>30</output>

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

<gadget id="calculator">(2/7) * 4</gadget>
<output>8/7 = around 1.142857</output>

<gadget id="calculator">2 - (8/7)</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">30 / (6/7)</gadget>
<output>35</output>

<result>35</result>