There were 120/3 = <<120/3=40>>40 men at the party.
There were 120/2 = <<120/2=60>>60 women at the party.
So, there were 40 + 60 = <<40+60=100>>100 men and women at the party.
Thus, 120 - 100 = <<120-100=20>>20 were children.
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