Subtract the sum of 2.8 and 1.5 from X, the difference is 8.07, find x.
X减去2.8与1.5的和，差是8.07，求x．
<gadget id="calculator">2.8 + 1.5</gadget>
<output>4.3</output>

<gadget id="calculator">8.07 + 4.3</gadget>
<output>12.37</output>

<result>12.37</result>