human
Cars have lined up on the motorway. Some of the cars drive through in the first 15 minutes of the traffic jam, then 20 more cars drive through in the remaining 15 minutes of the jam. 5 cars from the line take an exit so they don't have to drive through the traffic jam. If there were originally 30 cars on the motorway, how many cars drove through the traffic jam in the first 15 minutes?
assistant
How many cars drove through the traffic jam in the first 15 minutes? ** The cars that exited do not need to be included so there were 30 original cars – 5 cars that exited = <<30-5=25>>25 cars that drove through the traffic jam.
How many cars drove through the traffic jam in the first 15 minutes? ** Most of the cars exited in the final 15 minutes so in the first 15 minutes, there must have been 25 total cars – 20 cars that drove through in the final 15 minutes = 5 cars that drove through the traffic jam.
#### 5