A number of athletes stand in a square array of 20 rows and 20 columns. Now remove 5 rows and 5 columns. How many people have been reduced?
若干名运动员站成20行20列的方阵，现在去掉5行5列，共减了多少人．
<gadget id="calculator">20 * 20</gadget>
<output>400</output>

<gadget id="calculator">20 - 5</gadget>
<output>15</output>

<gadget id="calculator">15 * 15</gadget>
<output>225</output>

<gadget id="calculator">400 - 225</gadget>
<output>175</output>

<result>175</result>