The average of three numbers is 4.2, the first number is 4.25, the second number is 0.3 more than the third number, what is the third number
三个数的平均数是4.2，期中第一个数是4.25，第二个数比第三个数多0.3，第三个数是多少
<gadget id="calculator">4.2 * 3</gadget>
<output>12.6</output>

<gadget id="calculator">12.6 - 4.25 - 0.3</gadget>
<output>8.05</output>

<gadget id="calculator">8.05 / 2</gadget>
<output>4.025</output>

<result>4.025</result>