Level 3
Adam and Bryan builds a toy car in 4 hours.
Bryan and Chris builds a toy car in 6 hours.
Chris and Adam builds a toy car in 3 hours.
How long does it take for Adam, Bryan and Chris to build a toy car together?
Level 2
Adam has some stickers.
He gives away equal number of stickers each day.
After 5 days,
he has 23 of the stickers left.
After another 7 days, he has 21 stickers left.
How many stickers does he have at first?