When a=5, b=4, what is 3.2a-2.4b=
当a=5，b=4时，3.2a-2.4b=多少
<gadget id="calculator">3.2 * 5</gadget>
<output>16</output>

<gadget id="calculator">2.4 * 4</gadget>
<output>9.6</output>

<gadget id="calculator">16 - 9.6</gadget>
<output>6.4</output>

<result>6.4</result>