giải bài toán bằng cách lập phương trình 1, hai vòi nước cùng chảy vào một bể (bể cạn) thì sau 12h đầy bể . người ta mở cho cả hai vòi cùng chảy trong 4h rồi tắt vòi thứ nhất , chỉ mở vòi thứ hai thì 10h sau đầy bể . hỏi nếu để riêng mỗi vòi chảy thì sau bao lâu sẽ đầy bể

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1. The last time she wrote to me was in March. => She …………… 2. Mrs.Linh started to teach the children in that remote village two years ago. => Mrs. Linh ……………….. 3. It’s seven years since Nhi and Bin were married. => Nhi and Bin ……………… 4. The last time she visited me was 5 months ago. => She …………………… 5. I last had my hair cut when I left her. => I ……….. 6. I last saw my aunt before the beginning of the Covid-19. => I …………. 7. I started learning English when I was in grade 3. => I …………… 8. We last visited Ho Chi Minh city 3 years ago. => We ……… 9. The last time I met her was three years ago. => I ……………….. 10. David had gone home before we arrived. => After ………………. 11. We had lunch then we took a look around the shops. => Before …………………….. 12. My father had watered all the plants in the garden by the time my mother came home. => After …………………. 13. They (come) …………….. back home after they (finish) ………………… their work. 14. She said that she ( meet) ……………………. Mr. Bean before. 15.Before he (go) ………………………….. to bed, he (read) ………………………… a novel. 16. He told me he (not/wear) ………………………… such kind of clothes before. 17.When I (come) …………….. to the stadium, the match (start) …………. 18. Before she (listen) ………………….. to music, she (do)……………………. homework. 19. Last night, Peter (go) ………………….. to the supermarket before he (go) ………………… home. 20. He ......................... out when I came into the house.