How to solve the equation 2x-3 = 5x-21

2x-3=5x-21
2x-5x=3-21
-3x=-18
x=6

If the solution of equation 3ax-2 = 2x about X is less than that of equation 5x + 1 = 2x-11 by 2, the value of a is obtained

5x+1=2x-11
5x-2x=-11-1
3x=-12
x=-4
The solution x = - 6 of 3ax-2 = 2x
-6*3a-2=-12
18a=10
a=5/9

Master Wang planned to finish the work in five hours, but he finished it in four hours. How much has Master Wang improved his efficiency?

The time ratio between the plan and the actual is 5:4, and the efficiency ratio is 4:5,
The actual efficiency is (5-4)) △ 4 = 25% higher than that of the plan

What is the quotient of the difference between 27.8 and 9.5 and the sum division of 1.6 and 3.5?
2 / 5 of a number plus 24 is exactly equal to itself. What is the number?
Simple calculation (writing process)
8/9×（3/4-（7/16-1/4））
1/5=（6/5×（3/4-7/12））

The difference between 1.27.8 and 9.5: 27.8-9.5 = 22.31.6 and the sum of 3 and 2 / 5: 1.6 + 3 and 2 / 5 = 1.6 + 5.5 = 7.1A divided by B: A / b = 22.3 / 7.1 = calculate by yourself, but I tend to think that you copied wrong: 3 and 2 / 5 should be 3 and 5 / 2? 2

Draw the largest circle in a square with a side length of 20 cm. What is the area of the circle______ Square centimeter

3.14 × (20 △ 2) 2, = 3.14 × 100, = 314 (square centimeter); answer: the area of this circle is 314 square centimeter

Evaluation: (1) if a and B are non-zero rational numbers, and a | a | + B | B | = 0, find the value of ab | ab |; (2) it is known that a is the smallest positive integer, B and C are rational numbers, and | 2 + B | + (3a + 2C) 2 = 0. Find the value of formula 4ac + c-a2 + C2 + 4

(1) ∵ A and B are non-zero rational numbers, a | a | + B | B | = 0, ∵ ab | ab | = - 1; (2) ∵ A is the smallest positive integer, | 2 + B | + (3a + 2C) 2 = 0, ∵ a = 1, 2 + B = 0, 3A + 2C = 0, ∵ a = 1, B = - 2, C = - 32, ∵ 4ac + c-a2 + C2 + 4 = 4 × 1 × (- 32) - 32-12 + (- 32) 2 + 4 = - 107

Some practical problems
1. There are two kinds of flowers, Lily and rose. 3 / 4 of lily is equal to 5 / 12 of rose. 2 / 5 of lily is 45 more than 1 / 12 of rose. How many Lily and rose?
2. An express train from station a to station B runs at 65.5km per hour. After one hour, another slow train runs at 58.5km per hour from station A. when the express train arrives at station B, the slow train is 104KM away from station B. how many kilometers is the distance between station a and station B?
3. If 12x-9y = 21,12y + 9x = 72, then x = (), y = ()
4. The passenger car starts from place a, and the freight car starts from place B opposite to the passenger car at the same time. After 10 hours, the passenger car is still 1 / 10 of the whole distance from place B, and the freight car exceeds the midpoint of 78 kilometers. It is known that the passenger car travels 4 kilometers more than the freight car every hour. How about the distance between Party A and Party B?

1.5/12 △ 3 / 4 = 5 / 9 rose is "1" lily "5 / 9" 2 / 5 * 5 / 9 = 2 / 9 45 / (2 / 9-1 / 12) = 324 rose 324 * 5 / 9 = 180 Lily 2.104-65.5 = 38.5km, the distance difference is 38.5 / (65.5-58.5) = 5.5hours, the idle time is 5.5 * 58.5 + 104 = 425.75km 3. X = 4, y = 34.10hours

As shown in Figure 1, there are two squares, one big and the other small. The distance between the corresponding sides is 1 cm. If the area between the two squares is 12 square centimeters, what is the area of the big square?

(12-1 × 1 × 4) △ 4 △ 1 = (12-4) △ 4 △ 1 = 8 △ 4 △ 1 = 2 (CM) 2 × 2 + 12 = 4 + 12 = 16 (square cm) a: the area of a large square is 16 square cm

A planet is 1.3 × 10 6 km away from the earth. How many seconds after the laser signal is sent from the earth to the planet, the return signal can be received

t=s/v=2*1.3*10^6/3*10^5=8.67s

acoustics
If you tap on the other end of a long steel pipe, how many times can you hear the sound on the other side?

The propagation speed of sound in different media is different. In your topic, there are two media, one is the steel tube itself, and the other is the air around the steel tube. Because they are two different media, you will hear the sound twice

How to solve the equation 2x-3 = 5x-21