After a number increases by 12.5%, it is exactly 40.5 (4/5), find this number. (solution by equation)
一个数增加12.5%以后正好是40.5的(4/5)，求这个数．(用方程解)
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">40.5 * (4/5)</gadget>
<output>32.4</output>

<gadget id="calculator">12.5 / 100</gadget>
<output>0.125</output>

<gadget id="calculator">1 + 0.125</gadget>
<output>1.125</output>

<gadget id="calculator">32.4 / 1.125</gadget>
<output>28.8</output>

<result>28.8</result>