When □=2.1, 4*□-0.4=△, then 6(△+0.5)=how much.
当□=2.1时，4*□-0.4=△，那么6(△+0.5)=多少．
<gadget id="calculator">4 * 2.1</gadget>
<output>8.4</output>

<gadget id="calculator">8.4 - 0.4</gadget>
<output>8</output>

<gadget id="calculator">8 + 0.5</gadget>
<output>8.5</output>

<gadget id="calculator">6 * 8.5</gadget>
<output>51</output>

<result>51</result>