x-20=40
2: Cup A contains 400 ml of water, which is 2.5 times that of Cup B. How many ml of water is there in Cup B?
2.5x=400
3: The bus stopped, 17 people got off and 12 people got on. There are 35 people in the car now. How many people are there on the bus?
x- 17+ 12=35
4.9 cars came to the parking lot first, and then 24 cars were taken away. Now there are only six cars left. How many cars are there in the parking lot?
x+9-24=6
5. There are 188 students in Grade Three, which is three times more than Class Four (1). How many students are there in Class Four (1)?
3x+4 1= 188
At 6: 00, there are 49 students in Class 4 (1), which is 39 fewer than Class 4 (2). How many students are there in Class Four (2)?
2x-39=49
7: The earth goes around the sun for about 365 days, which is four times longer than the time 13 for Mercury to go around the sun. How many days does it take for Mercury to go around the sun?
4x+ 13=365
8: The height of Building A is 492 meters, which is 54 meters less than 7 times the height of Building B.. What is the height of building B?
7x-54=492
9: 3.5 times a number is 2.5 times less than 20. What's this number?
3.5x=20-3.5
10: Little Dingding bought two notebooks and a ballpoint pen. The unit price of a notebook is twice that of a ballpoint pen, and Dingding Jr. bought the notebook at the expense of 6 yuan. What is the unit price of ballpoint pen?
2× 2x=6
The equations are listed and the solution method is omitted. Please adopt!