Question
There were 3 times as many boys as girls in the classroom at first. After 3 boys left and 4 girls entered the classroom, there were 9 more boys than girls remaining in the classroom. What was the number of boys in the classroom at first?
4 m

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There were 3 times as many boys as girls in the classroom at first. After 3 boys left and 4 girls entered the classroom, there were 9 more boys than girls remaining in the classroom. What was the number of boys in the classroom at first?