Class C gets x+24 books.

The assignment of class b is x+24- 12=x+ 12.

Class a includes: x+x+24+x+ 12= 180.

3x+36= 180

x=( 180-36)÷3

X=48 (Ben)

Class b: 48+ 12=60 (Ben)

Class C: 48+24=72 (Ben)

Their ratio is -A: B: C =48:60:72=4:5:6.

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