There were some boys and girls in a room. If 24 boys leave the room, the total number of students who remained in the room will be 7 times the number of boys who remained in the room. If 12 girls leave the room, the total number of students who remained in the room will be 4 times the number of boys. How many students were there in the classroom?
[24][1 u][ 6 u ]
[ ][ ][ ][ ][12]
[24][1 u][24][1 u][24][1 u]
Redraw the girl units (using boy unit)
3 u --> 24 x 3 + 12 = 84 Compare the girls (in red)
1 u --> 84 ÷ 3 = 28
7 u --> 7 x 28 = 196
196 + 24 = 220 students
There were 220 students in the class.
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