Số can 2l là:
  (126 - 8 x 10 - 6 x 5) : 2 = 8 (can)
Nếu thay bằng các can 4l thì cần số can là:

 8 x 2 : 4 = 4 (can)

                Đáp số: 4 can.

Đổi 2 giờ 30 phút = 2,5 giờ 

Sau 2 giờ 30 phút , xe máy đi được số ki-lô-mét là : 

 42 x 2,5 = 105 ( km )

Khi đó xe máy còn cách B số ki-lô-mét là : 

135 - 105 = 25 ( km )

Vậy xe máy còn cách B 25 km

dose

1. After/when they had eaten dinner, Mark cleared the table.

2. After/when Rita had taken a hot bath, she felt much better.

3. When/after he had painted the hall and the kitchen, Jack decided to have a rest.

4. After/when they had won the match, they went to a pub to celebrate it.

5. After/when the robbers had left, the bank clerk called the police.

6. After/when I had finished reading the magazine, I lent it to Sophie.

7. After/when Lisa had tried on five sweaters, she finally took the red one.

8. After/when he had finished eating, Peter asked for a cup of coffee.

9. After/when she had completely recovered, Mandy could leave the hospital.

10. After/when they had done their homework, they could play PC games.