In a PE class, the whole class is arranged in four lines, each line has the same number of people. The position of Xiaofang row is the sixth from the front and the seventh from the back. How many students are there

In a PE class, the whole class is arranged in four lines, each line has the same number of people. The position of Xiaofang row is the sixth from the front and the seventh from the back. How many students are there

The position of Xiaofang row is the sixth from the front and the seventh from the back, so each row has: 6 + 7-1 = 12 (people)
So there are 12 * 4 = 48 (people)

Class five (1) does radio exercises. The class is divided into four lines. The number of people in each line is equal
How many people

Xiaohua is the fifth from the front, indicating that there are four people in front of Xiaohua and the eighth from the back, indicating that there are seven people behind Xiaohua. In addition, Xiaohua has a total of 4 + 7 + 1 = 12 people
So there are 12 people in one line, and there are four lines
So the total number is 12 × 4 = 48

How many students are there in a class with four equal rows in PE class?

Given that the first six and the last seven in a row are the same person, then the row is 12
Known that there are four rows, and the number of equal, then the class a total of 48 people

It is known that the mass of an oxygen atom is 2.657 * 10 ^ - 26kg. Please calculate the molar mass of O2? Online and so on. Step by step analysis is needed
I'm confused about chemistry. The clearer the better. I can score. Thank you

We know that the number of 1mol oxygen is 6.02x10 to the 23rd power, so the mass of 1mol oxygen is 0
657 * 10 ^ - 26 x6.02x * 10 ^ - 23x2 = 32x10-3kg = 32g, that is, the mass of 1mol oxygen is 32g, then the molar mass is 32g / mol

It is known that the mass of an iron atom is 9.288 * 10-26 power kg, and the mass of a carbon 12 atom is 1.993 * 10-26 power kg

Define 1 / 12 of carbon 12 as a standard measurement
1.993*10-26/12=1.66*10-27
And then we use the mass of iron as a starting point. How many parts there are are is the relative atomic mass
Science and technology law, remove the following decimal 92.88 / 1.66 = 55.95. That's the origin of 56 that we usually remember~

The square of equation x + 6x + 9 = 0,

Square of X + 6x + 9 = 0
x²+6x+3²=0
（x+3）²=0
So:
x+3=0
So:
x= -3

Solving the equation x squared minus 6x + 5 = 0 by collocation method

x2-6x+5=0
x2-6x+9-4=0
(x2-6x+9)-4=0
(x-3)2-4=0
(x-3)2=4
x=5

Solution equation: x square + 6x + 44 / 5

X = [- 6 + - radical (6 ^ 2-4 * 44 / 5)] / 2
X = [- 6 + - radical 36-176 / 5] / 2
=[- 6 + - 2 / radical 5] / 2
=-3 + - 1 / radical 5
X1 = - 3 + (radical 5) / 5
X2 = - 3 - (radical 5) / 5

Solving the equation: the square of X + 6x + 5 = 0

x*2＋6x=-5
X * 2 plus 6x plus 9 = - 5 plus 9
(x + 3) * 2 = 4
X + 3 = 2 or x + 3 = - 2
x1=-1 x2=-5
(I can't send a plus sign on my mobile phone)

1 / 5 (5 + x) = 6x-7 to solve the equation

1/5(5+x)=6x-7
1/5×5＋1/5×x＝6x－7
1＋1/5x＝6x－7
6x－1/5x＝1＋7
29/5x＝8
x＝8÷29/5
x＝40/29