Robert coughs twice as much as Georgia who coughs 5 times so Robert coughs 2*5 = <<10=10>>10 coughs per minute
Georgia coughs 5 times and Robert coughs 10 times so together they cough 5+10 = <<5+10=15>>15 times per minute
After 20 minutes they will have coughed 15*20 = <<15*20=300>>300 coughs
#### 300