Solving problems by solving equations 1. There are 874 seats in the school auditorium, with a total of 23 rows. Each row has the same number of seats. How many seats are there in each row?

Solving problems by solving equations 1. There are 874 seats in the school auditorium, with a total of 23 rows. Each row has the same number of seats. How many seats are there in each row?

874 / 23 = 38

In Library A and B, there are as many books as there are in the two bookshelves. Later, 38 books were added to bookshelf a, and 72 books were borrowed from bookshelf B. at this time, the books in bookshelf a are three times as many as those in bookshelf B. how many books were there in each bookshelf? (Note:)

If there are x books on shelf B, then there are 3x books on shelf a
x+38=3x-72
1+38=3x-x-72
39=2x-72
39+72=2x-72+72
111=2x
111 divided by 2 = 2x divided by 2
x=55.5

Applied knowledge of Mathematics
The buildings left behind in ancient times will be inclined, bent and deformed due to the long-term bearing of self weight, temperature, wind and other factors. In order to protect these buildings, the cultural relics department timely observed them and understood various row variables. An ancient tower was observed. The x-axis is east-west direction, and the Y-axis is north-south direction, The z-axis is vertically upward. (coordinate unit: give the method to determine the deformation of the ancient pagoda

Take the center of the tower bottom as the intersection of X and Y axes, take the top of the tower as a point on Z axis, and make a vertical line to point to the ground. If it does not coincide with the intersection of the ground, it is deformation

Who can help me find the next expression. Plus symbols
For example, red phosphorus + oxygen (ignite) phosphorus pentoxide
Symbol P + O2 (ignite) P2O5... Who will,
Oxygen production. O2 3
Burning c.s.p Mg.Fe Ethanol (C2H5OH)
Heating. Hg 1

Potassium chlorate (heating with manganese dioxide) → potassium chloride + oxygen KClO3 MnO2 kclo2 potassium permanganate (heating) → potassium manganate + manganese dioxide + oxygen KMnO4 k2mno4 MnO2 O2 hydrogen peroxide (manganese dioxide) → water + oxygen H2O2 MnO2 H2O2 ignite me to save carbon + oxygen → carbon dioxide CO2 CO2 CO2 sulfur

How to write the chemical symbol expression of grade three
Is it just to replace the name in the literal expression with a symbol? What's the difference with chemical equation?

The literal expression is to use the Chinese of reactants and products, plus the right arrow, which indicates the reaction conditions
Chemical equations are represented by elemental symbols

It's better to take literal phenomena and literal expressions

1、 Synthesis reaction 1. Magnesium burning in air: 2mg + O2 = ignition = 2MgO phenomenon: (1) emit dazzling white light (2) release heat (3) generate white powder (2) iron burning in oxygen: 3Fe + 2O2 = ignition = Fe3O4 phenomenon: (1) intense combustion, Martian emission (2) release heat (3) generate a

Find any alphanumeric and symbol of regular expression except Chinese
Contains the following characters
abcABC123./*-~@#%^&*(_ )"|:>

[\u4e00-\u9fa5]+
This regular expression matches more than one Chinese character, as long as the matching result is false, it is non Chinese

JS regular expression can only input 4-20 lowercase alphanumeric or Chinese characters, other symbols and spaces can't enter anything

[a-z0-9\u4E00-\u9FFF]{4,20}

Requirements for finding a cipher regular expression: the combination of more than 10 digits + letters + special symbols requires two writing methods in C # and JS

::[^\u4e00-\u9fa5\d\w]+\d+[\w\W]+[^\u4e00-\u9fa5]*)|(?:[^\u4e00-\u9fa5\d\w]+[\w\W]+\d+[^\u4e00-\u9fa5]*)|(?:\d+[^\u4e00-\u9fa5\d\w]+[\w\W]+[^\u4e00-\u9fa5]*)|(?:\d+[\w\W]+[^\u4e00-\u9fa5\d\w]+[^\u4e00...