It is known that 0.8a-4=8, then 0.8*(a-4)=how much.
已知0.8a-4=8，那么0.8*(a-4)=多少．
<gadget id="calculator">15 - 4</gadget>
<output>11</output>

<gadget id="calculator">0.8 * 11</gadget>
<output>8.8</output>

<result>8.8</result>