Question
At first, there were 408 more girls than boys at the concert hall. By 1 p.m., a total of 276 girls and boys left the concert hall. There were as many girls as boys who left the concert hall. In the end, there were 4 times as many girls as boys who remained behind. How many girls were at the concert hall at first?
4 m

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At first, there were 408 more girls than boys at the concert hall. By 1 p.m., a total of 276 girls and boys left the concert hall. There were as many girls as boys who left the concert hall. In the end, there were 4 times as many girls as boys who remained behind. How many girls were at the concert hall at first?