What is the quotient obtained by dividing 6.4 by the difference between 2.1 and 0.5? What is the correct column
6.4除以2.1与0.5的差，所得的商是多少？正确的列式是多少
<gadget id="calculator">2.1 - 0.5</gadget>
<output>1.6</output>

<gadget id="calculator">6.4 / 1.6</gadget>
<output>4</output>

<result>4</result>