There are 140 books in a library. Literature and art books are 80% of other books. How many are there?

There are 140 books in a library. Literature and art books are 80% of other books. How many are there?

Solution 1: set the other books in the library as X books
x+0.8x=140
The solution is x = 78
Literature and art books: 0.8x = 62
Solution 2: set the library literature and art books as y books
y+(5/4)y=140
The solution is y = 62
A: there are 62 books on literature and art

There are 75 science and technology books in the book corner of class 63. The number of literature and art books is 15 less than that of science and technology books?

Science and technology book: 75 literature and Art Book: 60
75-60=15
15 divided by 75 = 0.2 = 20%

Mr. Zhang bought books for the library. If he bought six fairy tale books and seven story books, it would cost 144 yuan. If he bought nine fairy tale books and seven same story books, it would cost 174 yuan
How much does it cost to buy a fairy tale book and a story book

174-144 = 30 yuan
A fairy tale book: 30 / 3 = 10 yuan
144-6 * 10 = 84 yuan
A story book: 84 / 7 = 12 yuan

Reading answers to book loving Dad
I practice every day,

My father loves to buy books. He is an ordinary worker. He likes to smoke, drink, read and buy books. He always drinks bad wine and smokes bad cigarettes, but he has a high taste in buying books. From the historical records of China, the chronicles of the Three Kingdoms, the chronicles of the Eastern Zhou Dynasty to the miserable world, war and peace, how is steel made in foreign countries

How do you know if it means finding the opposite number or just a sign

It can be regarded as a symbol in the title

If the domain of F (x) is [- 2,3], find the domain of F (log2 (2x + 3))

The definition field bit of F (x) [- 2,3]
Then - 2 ≤ log2 (2x + 3) ≤ 3
1/4≤2x+3≤8
-11/2x≤5/2
therefore
The domain of F (log2 (2x + 3)) [- 11 / 2,5 / 2]

Proof: x = (- B ± √ B ^ 2-4ac) / 2A the gods help
It is proved that: x = (- B ± √ B ^ 2-4ac) / 2a, the more detailed the better,

ax^2+bx+c=0 --->ax^2+bx=-c --->x^2+bx/a=-c/a --->x^2+2(b/2a)x+b^2/(2a)^2=-c/a+b^2/(4a^2) --->[x+b/(2a)]^2=(b^2-4ac)/(2a)^2 --->x+b/(2a)=+'-√(b^2-4ac)/2a --->x=[-b+'-√(b^2-4ac)]/(2a).
Please accept

Find the common number set represented by symbol

N natural number set, N + positive integer set, Z integer set, r real number set

How to pronounce the word "fiber", like fiber and fiber, and whether to pronounce it as Xian or Qian,

It means that everything in silk is read
Mr. Qian

Analytic geometry (line and circle)
When a is any real number, if the straight line ax-y-2 (a + 1) = 0 passes through the fixed point m, then the equation of the circle with m as the center and circumscribed with the circle x ^ 2 + y ^ 2 + 2x-4y + 1 = 0 is__________ .
(x-2)^2+(y+2)^2=9】

The straight line ax-y-2 (a + 1) = 0A (X-2) = y + 2, so when X-2 = 0, there is y + 2 = 0, that is, x = 2, y = - 2, that is, the constant crossing point m (2, - 2) circle x ^ 2 + y ^ 2 + 2x-4y + 1 = 0, that is, (x + 1) ^ 2 + (Y-2) ^ 2 = 4, the center coordinates of the circle are (- 1,2), the center distance of the two circles = root sign [(2 + 1) ^ 2 + (2 + 2) ^ 2] = 5 phase circumtangent, then the radius of the circle r = 5-2 = 3, so the equation is (...)