For the project, a 1,200-meter-long canal has been repaired for 15 days, with 50 meters being repaired every day. How many meters are left unrepaired?
工程对要修一条长1200米的水渠，已经修了15天，每天修50米．还剩多少米没修？
<gadget id="calculator">50 * 15</gadget>
<output>750</output>

<gadget id="calculator">1_200 - 750</gadget>
<output>450</output>

<result>450</result>