8-x = 3.21 solve the above equation

8-x = 3.21 solve the above equation

X=8-3.12
X=4.88

The proportion of solution: (1) x: 21 = 6:14 (2) 4:0.3 = x: 1.8 (3) 2 / 3 = 9 / 9 x (4) x: 4 / 5 = 5 / 10 of 12

（1）x：21=6:14
x=21×6÷14=9
（2）4:0.3=x：1.8
x=4×1.8÷0.3=24
(3) 2 / 3 = x / 9
x=2/3×9=6
(4) X: 4 / 5 = 5 / 12: 10
x=4/5×5/12÷10=1/30

Three fourths of a number is equal to 40% of 50. What is the number

This number is X
3/4x=50x40%
3/4x=20
x=80/3

Given the set a = {x | A-1 ＜ x ＜ 2A}, B = {x | 0 ＜ x ＜ 2} (1) when a = B, find the value set of the real number a; (2) when a is a subset of B
The known set a = {x | A-1 ＜ x ＜ 2A}, B = {x | 0 ＜ x ＜ 2}
(1) When a = B, find the value set of real number a;
(2) When set a is a subset of set B, the value of real number a is calculated

1) a-1=0,2a=2
a=1
2) 1.A=∅
2a≤a-1
a≤-1
2.a-1≥0,2a≤2
a≥1,a≤1
That is, a = 1
therefore
The range of a is a ≤ - 1 or a = 1
The set is {a | a ≤ - 1 or a = 1}

It takes 10 hours for a bus to go from city a to city B, and 15 hours for a truck to go from city B to city A. the two cars leave each other at the same time. When they meet, the bus is 240 kilometers away from city B. how many kilometers are there between city a and city B?

A: the distance between city a and city B is 600 km

Given the fraction (3N ^ 2 + 7n + 7) / (2 + n), the simplified result is an integer. What are the integers n that meet the requirements?

The original formula = (3N & sup2; + 7n + 2 + 5) / (n + 2)
=[(n+2)(3n+1)+5]/(n+2)
=3N + 1 + 5 / (n + 2) is an integer, then n + 2 is a divisor of 5
So n + 2 = 1, - 1,5, - 5
So n = - 1, - 3,3, - 8

What's the percentage of 5-hour journey (2 / 5) and 4-hour journey?
What's 15% less than 40

2/5/5=2/25 2/25*4=8/25 40-40*15%=40*85%=34

How much is 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 +. 100?

Let s = 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 +. 100
Then s can also be equal to s = 100 +. + 10 + 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1
Add the two formulas
2S = 101 + 101 +. 101 total 100
So 2S = 100x101
S=50x101=5050.

Write a passage about the likeness of the universe, the earth and the moon

The earth is your father. The moon is just like your mother. It always stands behind your father and lights up when he is facing the dark. You are their universe and can't escape from your Wuzhishan

Subtract one half from seven times of a number to get one half. Find the number

Let X be the number
7x-1/2=1/2
7x=1/2+1/2
7x=1
x=1/7
This number is one in seven
Hope to help you