Write the three formulas 357/21=17; 6+15=21; 400-43=357 into a comprehensive formula: how much.
把357/21=17；6+15=21；400-43=357这三个算式写成一个综合算式：多少．
<gadget id="calculator">400 - 43</gadget>
<output>357</output>

<gadget id="calculator">6 + 15</gadget>
<output>21</output>

<gadget id="calculator">357 / 21</gadget>
<output>17</output>

<result>17</result>