Subtract the sum of 3.5 and 4.7 from 21, multiply the difference by 1.5, what is the product?
21减去3.5与4.7的和，所得的差乘1.5，积是多少？
<gadget id="calculator">3.5 + 4.7</gadget>
<output>8.2</output>

<gadget id="calculator">21 - 8.2</gadget>
<output>12.8</output>

<gadget id="calculator">12.8 * 1.5</gadget>
<output>19.2</output>

<result>19.2</result>