There were 72/2 = <<72/2=36>>36 laptops sold.
There were 72/3 = <<72/3=24>>24 netbooks sold.
So, there were a total of 36 + 24 = <<36+24=60>>60 laptops and netbooks sold.
Thus, 72 - 60 = <<72-60=12>>12 desktop computers were sold last month.
#### 12