When a=2.8, b=6.3, find the value of 3a+2b.
当a=2.8，b=6.3时，求3a+2b的值．
<gadget id="calculator">3 * 2.8</gadget>
<output>8.4</output>

<gadget id="calculator">2 * 6.3</gadget>
<output>12.6</output>

<gadget id="calculator">8.4 + 12.6</gadget>
<output>21</output>

<result>21</result>