When a=6.8, b=4.5, what is the value of 5a-4b?
当a=6.8，b=4.5时，则5a-4b的值是多少．
<gadget id="calculator">5 * 6.8</gadget>
<output>34</output>

<gadget id="calculator">4 * 4.5</gadget>
<output>18</output>

<gadget id="calculator">34 - 18</gadget>
<output>16</output>

<result>16</result>