4. Solution: Suppose the population of another village is XX (2x-3) = 834x2x-3 = 8343x = 837x = 279. Larger villages: 934-279=555 (people). 5. Solution: Suppose it took B x time10 (x =15x10x300 =15x10x-15x =-300-5x =-300. 2 (5x20) = 2981/2x5/2x10 = 2983x10 = 2983x = 288x = 96 The speed of the maglev train is: 96 times 5 20=5007: Solution: Let the windless wind speed be x, Then the downwind speed is (x2), the headwind speed is (x-24)2 hours and 50 minutes = 17/6 hours 654336x=- 140x=840, and the voyage is 3x (840-24) = 3x816 = 2448 (. 9. Solution: Suppose X people do it for 2 hours, and 2/80X 8/80(X 5)=3/4 (since this problem, I won't write the process. Then buy black cloth (138-X) and Russian ruler 3X 5( 138-8)=540 to get 75.63 (two oh) 12 solution: suppose that B has x sheep and A has only x 21= 2 (x I'll call one by one) 13. Solution: suppose that the sales volume increases by x compared with the original price. It takes a long explanation to get 0.9 (1x) =1/9ke = 0.11increase1.1/solution: 2 = 36 = 36/2 (I copied the question 15). I'm so tired. Wow, I also said a lot. ==b The mathematical answer to this question in the first volume of grade seven is very difficult. I tried very hard to answer. Give me a satisfactory answer. /