(- 3.8) - (+ 7) who can do the subtraction of rational numbers?

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• 1. Find the first day of Mathematics (Centennial Dictionary) rational number subtraction that chapter of the title, in urgent need! Everyone help Only need the question, not the answer!
• 2. (simple calculation that can be simplified) (9) 1011 × (3 / 8 +) (10) 130 △ [(34-25) × 821] (11)205×32-656 (12)(20-1.25×0.8)÷1.9
• 3. 1.41.2×8.1+11×9.25+537×0.19 2.55555×666667+44445×666666-155555 3.0.4 × [11 / 52 △ 2 and 3 / 4 × (4.3-1.8)] × 26 4.（2×4×8×16×32）×（25×6.25×1.25×0.25） 5.85.42×7903.29-286.5×790.329+79032.9×4.323 6.1.135+2.246+3.346+4.475+5.557+6.768+7.768+8.979+9.979 7.1/18+1/54+1/108+1/270+1/378+1/504+1/648+1/810+1/990 8.（1+1）/2+（2-1）/2²+（3-1）/2³+… +The 100th power of (100-1) / 2 9.（1-1/2-1/3-… -1/1999）×（1/2+1/3+1/4+… +1/2000）-[（1-1/2-1/3-… -1/2000）（1/2+1/3+… +1/1999）] 10.20-{[（2²+1）/（2²-1）]+[（3²+1）/（3²-1）]+[（4²+1）/（4²-1）]+… +[（20²+1）/（20²-1）]}
• 4. Mathematics out of form calculation problem (can be simple to calculate) 4.56 + 37 + 4.44 + 47 23 - 8 / 9 × 3 / 8 △ 1 / 27 8.92×7.9+2.1×8.92+28.9 9/10×5/9+4/9×9/10+9/10
• 5. Practical questions (1 15:16:8) The ticket price of the quarter finals of 2002 World Cup announced by the Organizing Committee of South Korea is: 300 US dollars for the first-class seats, 200 US dollars for the second-class seats and 125 US dollars for the third-class seats. During the promotion activities, a shopping mall organized 36 award-winning customers to watch the quarter finals of 2002 World Cup in South Korea. After going out for other expenses, it plans to buy two kinds of tickets with 5025 US dollars (all the money is used up), Please design several schemes for the mall to choose, and explain the reasons
• 6. 11 and 13 Such as the title
• 7. It's from Jiangsu People's education press. Next semester. I'm sick and can't catch up
• 8. Word is not bad, reward points to how much!
• 9. If the sum of all the internal angles of a multilateral row and an external angle is 1000 degrees, then how many degrees is the external angle? How many sides is this row? Another question: the sides Ba and BC of the angle ABC are perpendicular to the sides ed and EF of the angle def, the perpendicular feet are m and N respectively, and the angle ABC = 60 degrees?
• 10. 8.9.10. 8. If you buy 10 jin eggs at a time, 20% discount is 3 yuan less than 10% discount, then the original price of 10 jin eggs is -------- yuan 9. The ratio of the three integers is 1:2:4, and their sum is 84. Then the largest number among the three integers is () A 56 B 48 C 36 D 12 10. To make a 5-meter-long and 3-meter-wide refrigerator without cover, the cost of box bottom is 60 yuan per square meter, and the cost of box wall per square meter is 2 / 3 of the cost of box bottom per square meter. If the total cost of the whole water tank is 1860 yuan, calculate the height of the water tank
• 11. What are the items in the formula 1 / 2-3 / 2-5 / 2-7 / 4?
• 12. Subtraction of rational numbers in the first year of junior high school: (1) given that the difference between 3 and a number is - 5, find the number. (2) write two negative numbers so that their difference is - 5, write the formula
• 13. ﹙1/4-5/9-1/3+7/12﹚÷﹙﹣1/36﹚
• 14. Mr. Liu said to Xiaotian, "my age 18 years ago is the same as your age 6 years later. Five years ago, my age was seven times your age. How old is Xiaotian this year?
• 15. Mr. Liu said to Xiaotian, "my age 18 years ago is the same as your age 6 years ago. Five years ago, my age was seven times your age. How old is Xiaotian this year?
• 16. 18.5 * 9 / 7 + 16.5 * 9 / 11-5 help the teacher 18.5 times 7 / 9 plus 16.5 times 11 / 9
• 17. 4/15×6/8= 3/8÷12= 4/5×5/6= 36×5/18= 4/15×6/8= 3/8÷12= 4/5×5/6= 36×5/18= 2/3÷6/5= 6/25×5/18= 7/8×24= 7/12×1/14= 3/7-1/8= 13/25×200= 7/25×51/21= 3-5/18= 5/21×63= 8/19+11/19= 64×5/16=?
• 18. 6 + 9 + 12 + 15 + 18 + for math problems +303 6+9+12+15+18+…… +303
• 19. The mileage of the railway from a to B is 480 km. From a to B, the train a with the word "g" and the train B with the word "d" can go directly to B. It is known that the average speed of train a is 40 km / h faster than that of train B, and the running time is 2 hours less than that of train B_____________ I can't ask the average speed and driving time of car a because I use my mobile phone to ask questions, Three hours or four hours
• 20. A shopping mall in Shenzhen bought a batch of Hainan watermelons before the Spring Festival. They can sell 500 kg a day and make a profit of 0.3 yuan per kg. In order to reduce the inventory as soon as possible, the shopping mall decided to take appropriate price reduction measures. The survey shows that when the sales price is reduced by 0.1 yuan, the sales volume will be increased by 100 kg per day. If the shopping mall wants to make an average profit of 120 yuan per day, how much should the price be reduced per kg of watermelons?