In a division formula with no remainder, the sum of the dividend and the divisor is 84, and the quotient is 20. What is the dividend?
在一个没有余数的除法算式中，被除数与除数的和是84，商是20，被除数是多少．
<gadget id="calculator">20 + 1</gadget>
<output>21</output>

<gadget id="calculator">84 / 21</gadget>
<output>4</output>

<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<result>80</result>