Analysis of the first question: (1) Suppose that Team A can lay X meters every day. According to the fact that the number of days required for team A to lay 350 meters is the same as that required for team B to lay 250 meters, the equation is solved. (2) If Y meters are allocated to Team A, they will be allocated to Team B (1000-y) meters. According to the fact that the time limit for completing the project does not exceed 10 days, the inequality group is analyzed. Solution: (1) If Team A can lay X meters every day, then Team B can lay (x-20) every day. The solution is x=70. Test: x = 70 is the solution of the original fractional equation. A: Construction teams A and B can lay 70 meters and 50 meters respectively every day. (2) If y meters are allocated to construction team A, they will be allocated to construction team B (1000-y) meters. According to the meaning of the question, the solution is 500 ≤ y ≤ Scheme 2: Team A is 600 meters and Team B is 400 meters; Option 3: Assign 700 meters to Team A and 300 meters to Team B. Option 2: (1) According to the meaning of the question, k=- 1. B = 120。 The expression of linear function is y =-x+ 120. (2 points) (2) w = (x-60) (-x+120) =-x2+180 x-7200. When x=87, W =-(87-90) 2+900 = 89 1. ∴ When the sales unit price is set to 87 yuan, the mall can get the maximum profit, that is, 89 1 yuan. (6 points) (3) Multiply W=500. X 1=70，x2 = 1 10。 (7 points) As can be seen from the figure, if the profit of this mall is not lower than that of 500 yuan, the sales unit price should be between 70 yuan and 1 10 yuan, while 60 yuan/Taiwan ≤x≤87 yuan/Taiwan, so the sales unit price should be. You can ask me if you don't understand.