Adam goes to school every day. On Monday he had 6 lessons of 30 minutes each, and on Tuesday he had 3 lessons of 1 hour each. On Wednesday, Adam spent twice as much time at school as on Tuesday. How much time in total did Adam spend at school during these 3 days, in hours?
On Monday Adam had 6 * 30 = 
<gadget id="calculator">6*30</gadget>
<output>180</output>
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 = 
<gadget id="calculator">2*3</gadget>
<output>6</output>
6 hours at school.
This means that during these three days Adam spent at school 3 + 3 + 6 = 
<gadget id="calculator">3+3+6</gadget>
<output>12</output>
12 hours.

<result>12</result>