There are three numbers, the average of A and B is 75, the average of B and C is 69, the average of A and C is 81, the average of A, B, and C is How many?
有三个数，甲数和乙数的平均数是75，乙数和丙数的平均数是69，甲数和丙数的平均数是81，甲、乙、丙这三个数的平均数是多少？
<gadget id="calculator">75 * 2</gadget>
<output>150</output>

<gadget id="calculator">69 * 2</gadget>
<output>138</output>

<gadget id="calculator">81 * 2</gadget>
<output>162</output>

<gadget id="calculator">150 + 138 + 162</gadget>
<output>450</output>

<gadget id="calculator">450 / 2</gadget>
<output>225</output>

<gadget id="calculator">225 / 3</gadget>
<output>75</output>

<result>75</result>