On Monday Adam had 6 * 30 = <<6*30=180>>180 minutes of lessons, which is 3 hours.
On Wednesday Adam spent twice as much time at school as on Tuesday, so he spent 2 * 3 = <<2*3=6>>6 hours at school.
This means that during these three days Adam spent at school 3 + 3 + 6 = <<3+3+6=12>>12 hours.
#### 12