First find the total wait time for the swings in minutes: 3 kids * 2 minutes/kid = <<3*2=6>>6 minutes
Then convert that number to seconds: 6 minutes * 60 seconds/minute = <<6*60=360>>360 seconds
Then find the total number of kids waiting for the slide: 3 kids * 2 = <<3*2=6>>6 kids
Then find the total wait time for the slide: 15 seconds/kid * 6 kids = 90 seconds
Then subtract the total wait for the slide from the total wait for the swings to find the difference: 360 seconds - 90 seconds = <<360-90=270>>270 seconds
#### 270