The sum, difference, and quotient obtained by adding, subtracting, and dividing a natural number to itself are exactly 81. what is this natural number
一个自然数与自己相加、相减、相除所得到的和、差、商三个数相加，恰好是81．这个自然数是多少
<gadget id="calculator">81 - 1</gadget>
<output>80</output>

<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<result>40</result>