A ribbon with a length of 20 meters is known to be subtracted by 3.8 meters for the first time, and each subsequent cut will be 1.6 meters longer than the previous one. How much rice is left after cutting three times?
一条长20米的彩带，已知第一次减去3.8米，以后每剪一次都比前一次多1.6米．剪三次后还剩多少米？
<gadget id="calculator">3.8 + 1.6</gadget>
<output>5.4</output>

<gadget id="calculator">1.6 * 2</gadget>
<output>3.2</output>

<gadget id="calculator">3.8 + 3.2</gadget>
<output>7</output>

<gadget id="calculator">20 - 3.8 - 5.4 - 7</gadget>
<output>3.8</output>

<result>3.8</result>