When a=5b=6c=7, what is the value of bc-ac
当a=5b=6c=7时，bc-ac的值是多少
<gadget id="calculator">6 * 7</gadget>
<output>42</output>

<gadget id="calculator">5 * 7</gadget>
<output>35</output>

<gadget id="calculator">42 - 35</gadget>
<output>7</output>

<result>7</result>