Andy is running late. School starts at 8:00 AM and it normally takes him 30 minutes to get there, but today he had to stop for 3 minutes each at 4 red lights and wait 10 minutes to get past construction. If he left his house at 7:15, how many minutes late will he be? Let's think first. Chain of thought:
First find how many minute Andy had to get to school when he left his house: 8:00 AM - 7:15 AM = 45 minutes. Then find the total time he spent waiting at red lights: 3 minutes / light * 4 lights = 12 minutes. Now add the normal travel time, red light time, and construction wait time to find Andy's total travel time: 30 minutes + 12 minutes + 10 minutes = 52 minutes. Now subtract the amount of time Andy had when he left his house from that number to find how many minute late he is: 52 minutes - 45 minutes = 7 minutes.
Therefore, the answer is 7.