Solution: Suppose there are X people in the painting group.
Then there are 56-x people in the calligraphy group and 64-(56-x)=8+x people in the singing group.
x+8+x=72
2x=64
x=32
Calligraphy group 56-32=24 people.
The singing group has 72-32=40 (people)
A: There are 24 people in the calligraphy group, 32 people in the painting group and 40 people in the singing group.
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