Girls in class

There are 12 more than boys, and the boys represent 30% of all pupils in the class. Find how many girls are in the class.

Final Answer:

d =  21

Step-by-step explanation:


d = 12 + c
c = 0.30 · (c+d)

c-d = -12
0.7c-0.3d = 0

Row 2 - 0.7 · Row 1 → Row 2
c-d = -12
0.4d = 8.4


d = 8.4/0.4 = 21
c = -12+d = -12+21 = 9

c = 9
d = 21

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