When a=4, b=1.5, how much is 5a-1.2b=.
当a=4，b=1.5时，5a-1.2b=多少．
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<gadget id="calculator">1.2 * 1.5</gadget>
<output>1.8</output>

<gadget id="calculator">20 - 1.8</gadget>
<output>18.2</output>

<result>18.2</result>