Then substitute x=-4 and y=- 1/2.
The second formula is equivalent to
- 12a+3 b+5008 =-3(4a-b)+5008 =-3 * 1000+5008 = 2008
2. You can catch up.
The car will take four people to the station first, and the other four will walk. The first four people can arrive in 10 minutes. The remaining four people walked 5/6 kilometers. There are still 55/6 kilometers to go. At this time, the car returned to pick up the remaining four people. Convert the speed to 1 km/s and112km/s respectively. (1+112) t = 55/6, which means that the car and people are in113. It takes them1113 minutes to get back to the station.
The total time spent is10+110/13+113.
Less than 28 minutes.
So we can get there.
You can ask again if you don't understand anything.