500 minus a number (4/7) is equal to the smallest three-digit number, find this number. (solution by equation)
500减去一个数的(4/7)等于最小的三位数，求这个数．(用方程解)
<gadget id="calculator">500 - 100</gadget>
<output>400</output>

<gadget id="calculator">7 / 4</gadget>
<output>7/4 = around 1.75</output>

<gadget id="calculator">400 * (7/4)</gadget>
<output>700</output>

<result>700</result>