The experimental primary school needs to build a 400-meter-long circular plastic runway, and 145 meters have been completed. The rest will be completed within 15 days. How many meters will be repaired on average per day?
实验小学要修一条长400米的环形塑胶跑道，已经完成了145米，剩下的要在15天之内完成，平均每天要修多少米？
<gadget id="calculator">400 - 145</gadget>
<output>255</output>

<gadget id="calculator">255 / 15</gadget>
<output>17</output>

<result>17</result>