The quotient of dividing two numbers is 5, and the difference between the numbers divided by two numbers is 8.4. What is the sum of these two numbers?
两个数相除的商是5，两个数相除的数的差是8.4，这两个数的和是多少．
<gadget id="calculator">5 - 1</gadget>
<output>4</output>

<gadget id="calculator">8.4 / 4</gadget>
<output>2.1</output>

<gadget id="calculator">2.1 * 5</gadget>
<output>10.5</output>

<gadget id="calculator">10.5 + 2.1</gadget>
<output>12.6</output>

<result>12.6</result>