First find the total time Karen spending grooming Rottweilers: 20 minutes/Rottweiler * 6 Rottweilers = <<20*6=120>>120 minutes
Then find the total time she spends grooming border collies: 10 minutes/border collie * 9 border collies = <<10*9=90>>90 minutes
Then add the time spent grooming all three kinds of dogs to find her total grooming time: 120 minutes + 90 minutes + 45 minutes = <<120+90+45=255>>255 minutes
#### 255