Lớp 9A và lớp 9B của một trường THCS dự định làm 90 chiếc đèn ông sao để tặng các em thiếu nhi nhân dịp Tết Trung Thu. Nếu lớp 9A làm trong 2 ngày và lớp 9B làm trong 1 ngày thì được 23 chiếc đèn; nếu lớp 9A làm trong 1 ngày và lớp 9B làm trong 2 ngày thì được 22 chiếc đèn. Biết rằng số đèn từng lớp làm được trong mỗi ngày là như nhau, hỏi nếu cả hai lớp cùng làm thì hết bao nhiêu ngày để hoàn thành công việc đã dự định ?

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Read the text and then choose the best answer A, B, C, or D. Visit the Edinburgh Festival Every year, thousands of people come to Edinburgh, the capital city of Scotland, to be part of the Edinburgh Festival. For three weeks every August and September the city is filled with actors and artists from all over the world. They come to Edinburgh for the biggest arts festival in Britain. During this time, the streets of the city are alive with music and dance from early in the morning untill late at night. You can even see artists painting pictures on the streets. Tens of thousands of tourists come to the festival to see new films and plays and to hear music played by famous musicians. This year, you can see over five hundred performances with actors from more than forty countries. The tickets for these performances are quite cheap, and it is usually easier to see your favourite star in Edinburgh than it is in London. So come to Edinburgh next summer! 16. How many people come to attend the Edinburgh Festival every year? A. Thousand people B. Thousands of people C. Some people D. Few people 17. How long does the Edinburgh Festival last? A. Two months B. Three months C. Three weeks D. For 3 weeks every August and September 18. What can you even see artists doing on the streets? A. Playing the guitar on the streets B. Singing songs on the streets C. Painting pictures on the streets D. Dancing on the streets 19. How many performances can people see this year? A. Tens of thousands B. Thousands C. Some people D. Over five hundred 20. How much are the tickets for these performances? A. Very cheap B. Very expensive C. Not cheap D. Not quite expensive