Solving engineering problems with linear equation of one variable To build a road, it takes 3 days for team a to do it alone, and 7 days for team B to do it alone. If team a and team B construct from both ends at the same time, how many days will it take to dig a good canal?

A work efficiency = 1 / 3
B efficiency = 1 / 7

Days required
=1 ÷ (1 / 3 + 1 / 7)
=10 / 21
=21 out of 10
=2.1 days

How can these problems be solved by linear equation with one variable
It takes 12 hours for a ship to return to land a. the velocity of the current is known to be 3 kilometers per hour. The velocity of the ship in still water can be calculated
There are 42 workers in 2 packaging factory. Each worker can produce 120 round iron sheets or 80 rectangular iron sheets per day on average. Two round iron sheets and one rectangular iron sheet can be used to make a sealed barrel. In order to make the products produced every day just match, how many workers should be assigned to produce round iron sheets and how many workers to produce rectangular iron sheets?
3 a car from a to B, the first third of the road section is ordinary highway, the rest is highway. It is known that the speed of the car on the ordinary highway is 60 km / h, and the speed on the highway is 100 km / h. The car from a to B has driven a total of 2.2 hours. How many kilometers are the ordinary highway and the highway?
There are two water inlet pipes (A and b) and one drainage pipe (c) in a reservoir. The reservoir can be filled after 6 hours of opening pipe a, 8 hours of opening pipe B, and 9 hours of opening pipe C. If pipe a and B are opened for two hours at the same time, and then pipe C is opened, how many hours after opening pipe C can the reservoir be filled?

1. Assuming that the speed of the vessel in still water is x km / h, then:
（x+3）×8=（x-3）×12
2. Suppose x workers should be assigned to produce round iron flakes
120×x=80×（42-x）×2
3. Assuming that the ordinary road section is x km, then:
x÷60+3x÷100=2.2
4. Assuming that the filled pool water is 1 and the pool water can be filled x hours after opening the C pipe, then:,
（1÷6+1÷8）×2+（1÷6+1÷8-1÷9）×x=1
In fact, these questions are very simple. If you find out how the above formula comes from, I don't think you need to ask similar questions in the future

The discount problem of linear equation with one variable
A shop will increase the price of a suit by 50% according to the cost price, and then sell it at a discount of 20% because of the holiday promotion. Each suit will be sold at 960 yuan. What is the cost price of this suit
How to set X, don't answer directly

Let the cost price be x yuan. According to the meaning of the question, (1 + 50%) x * 80% = 960,1.2x = 960, x = 800, we should understand the meaning of the question. According to the meaning of the question, we should list the equation. For example, this question is selling price = selling price. Pay attention to the unknown quantity of the equation. According to the question, it can be divided into direct setting and indirect setting

It is known that the focus of the ellipse is on the x-axis, the focal length is 4 / 3 √ 33, and the standard equation of the ellipse is obtained through the point (2,1)
I'll use it today and hand it in tomorrow

The standard equation of ellipse can be set as
x^2````y^2
----＋-----＝1 (a＞b＞0)
a^2````b^2
Its passing point (2,1) has two points
`4``````1
----＋-----＝1 (a＞b＞0)…… ①
a^2````b^2
If the focal length is 4 √ 33 / 3, there will be
2c＝4√33/3 →c^2＝44/3…… ②
And in the ellipse there is a ^ 2 = B ^ 2 + C ^ 2 ③
The results are as follows
3b^4＋29b^2－44＝0
→(b^2＋11)(3b^2－4)＝0
∴b^2＝4/3
Then a ^ 2 = 48 / 3
So the standard equation of ellipse is
x^2````y^2
----＋-----＝1
48/3```4/3

What is a general term formula of sequence 0,1,0, - 1,0,1,0, - 1

You can write piecewise functions
Or an = sin (n * π / 2)

#Define step [] {6,12,18,24,30,36,48,60,72,90120180360720} is this expression correct?

No problem
But it won't achieve the array function you want

What's the fraction of 24 decimeters to 5 meters? What's the simplest fraction?

5m = 50m
24÷50=12/25
A: 24 decimeters is 12 / 25 of 5 meters

Xiaohua plans to spend 10 days reading a 116 page science and technology book. In the first four days, she has read 44 pages. How many pages can she read every day
After a 200 yuan price cut, the price of a color TV is 1800 yuan, down%?

Xiaohua plans to spend 10 days reading a 116 page science and technology book. In the first four days, she has read 44 pages. How many pages can she read every day
(116-44) / (10-4) = 12 pages
After a 200 yuan price cut, the price of a color TV is 1800 yuan, down%?
200÷(200+1800)=10%
To adopt the correct answer first is to respect the labor of the respondent

To solve the equation, 1,17-4 (x + 0.5) = x 2,6-3 (x + 2 / 3) = 2 / 3,4 (15-2x) - 6x = 16x-6 (8-x)

17-4（x+0.5)=x
17-4x-2=x
15=5x
x=3

6-3 (x + 2 / 3) = 2 / 3 & nbsp;
That is, 6-3 (x + &;) = &;
6-3x-2=⅔
18-9x-6=2
9x=10
X = ten ninths

4（15-2x）-6x=16x-6(8-x）
60-8x-6x=16x-48+6x
60+48=8x+6x+16x+6x
108=36x
x=3

Divide a 6-meter-long rope into eight sections. How many parts of the total length of each section is () meters, and how many parts of each section is 1 meter?
emergency

Each section is one eighth of its length, three fourths of a meter, and four thirds of a meter

Solving engineering problems with linear equation of one variable To build a road, it takes 3 days for team a to do it alone, and 7 days for team B to do it alone. If team a and team B construct from both ends at the same time, how many days will it take to dig a good canal?