The average of the three numbers is 56.8. It is known that the first two numbers are 28 and 54.4 respectively. What is the third number?
三个数的平均数是56.8，已知前两个数分别是28和54.4，求第三个数是几？
<gadget id="calculator">56.8 * 3</gadget>
<output>170.4</output>

<gadget id="calculator">28 + 54.4</gadget>
<output>82.4</output>

<gadget id="calculator">170.4 - 82.4</gadget>
<output>88</output>

<result>88</result>