1 + 2 = 3 4 + 5 + 6 = 7 + 8 9 + 10 + 11 + 12 = 13 + 14 + 15. What is the 30th equation

1 + 2 = 3 4 + 5 + 6 = 7 + 8 9 + 10 + 11 + 12 = 13 + 14 + 15. What is the 30th equation

When n = 30, there are 61 numbers 900 + 901 + 902 + • • • • • • + 930 = 931 + 932 + • + 960

1: There are 20 equations: 1 + 2 = 3, 4 + 5 + 6 = 7 + 8, 9 + 10 + 11 + 12 = 13 + 14 + 15?
2: 1 / 1; 2 / 1,1 / 2; 3 / 1,2 / 2,1 / 3; 4 / 1,3 / 2,2 / 3,1 / 4.99/100 in which row and column

1. The number of digits in each formula is 3, 5, 7 The 19th equation has 3 + 2 * 18 = 39, and the first 19 have 19 * (3 + 39) / 2 = 399. The 20th equation starts from 400, and there are 39 + 2 numbers in total. There is one more on the left than on the right, so there are 21 on the left and 20 on the right. The left is from 400 to 420 and 21 * (400 + 420) / 2 = 8610, the right is from 421 to 440 and 20 * (421 + 440) / 2 = 8610
2. It can be seen from the observation that the arrangement of the nth row is n / 1, (n-1) / 2, (n-2) / 3 ,1/n.
The number of columns is equal to the fraction, and the subtracted number in the numerator is less than the denominator by 1

The solution ratio is 42: x = 4.8:16, 7:28 = 15; X two thirds: Six fifths = x: 20
Talk about the solution idea of the process, and how to calculate the solution ratio?

The inner product is equal to the outer product
4.8x=42*16 x=672/4.8=140
7x=28*15 x=420/7=60
6x/5=20*2/3 x=200/18=100/9

Two seventh (3Y + 7) = 2-three-thirds y how to solve the equation of first degree with one variable

In the elementary one variable linear equation 2 (3y-4) + 7 (4-y) = 4y-7 (4-y), find the value of Y

Just the answer?
The answer is y = 2

3Y / 2 + y + 4Y / 5 = 66,

3y/2+y+4y/5=66
15y+10y+8y=660
33y=660
y=20

Given that the solution of the system of equations x + by = 2x + 3Y = 7 is a linear equation of one variable, and X-Y = 1, then B =?

From the meaning of the title
x. Y satisfies x + by = 2, 2x + 3Y = 7, X-Y = 1
Solving equations
2x+3y=7
x-y=1
have to
x=2
y=1
Substituting x + by = 2
have to
2+b=2
b=0

Solving one variable linear equation 1-2 × / 3 = 3 × + 1 / 7-3

27/11

Help me to solve the linear equation of one variable 2 (χ + 1) - (χ + 5) - 2 {χ - 2 / 3} = 2 χ + 1

2（2χ+1）—（χ+5）—2｛χ—2/3｝=2χ+1
4x+2-x-5-2x+4/3=2x+1
4x-x-2x-2x=1-2+5-4/3
-x=8/3
x=-8/3

The value of the unknown which can make the left and right sides of the equation equal is called ()
A. Equation B. equation C. solution equation D. solution of equation

The value of the unknown which can make the left and right sides of the equation equal is called the solution of the equation