The difference between A and B is 20. The ratio of A and B is 7:2. What is the sum of A and B?
甲、乙两数相差20，甲数与乙数的比是7：2，甲、乙两数的和是多少？
<gadget id="calculator">7 - 2</gadget>
<output>5</output>

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

<gadget id="calculator">7 + 2</gadget>
<output>9</output>

<gadget id="calculator">4 * 9</gadget>
<output>36</output>

<result>36</result>