Li Hua read a story book. On the first day, he read 1 / 4 of the whole book. On the second day, he read the remaining 1 / 5. On the first day, he read 20 more pages than on the second day How many pages is the story book?

200 pages

Li Hua read a story book. On the first day, he read 25% of the whole book. On the second day, he read 2 more pages than on the first day. There are 20 pages left. How many pages are there in this book?

With page x, then
X=0.25x+0.25x+2+20
=44
So there are 44 pages

Li Hua read a story book. On the first day, he read 25% of the whole book. On the second day, he read two more pages than on the first day, and there were 20 pages left. How many pages are there in this book?
Please answer it this afternoon. It's better to have an explanation and a formula!

There are x pages in the book
25%x+25%x+2+20=x
The solution is x = 44

A kind of children's story book was delivered to the bookstore. It sold 30% on the first day, and 120% on the second day, 30 more than the first day. How many of these story books were delivered to the bookstore?

30% × 120% - 30%, = 30% × 6%, = 500 copies; a: there are 500 copies of this kind of story books from the bookstore

According to the basic properties of the fraction, we can draw the following conclusions: 1__ ,_ And_ Change the symbols in it____ The value of the fraction remains unchanged

According to the basic properties of the fraction, we can get the following conclusions: the (numerator), (denominator) and (fraction) symbols of the fraction, change the (two), the value of the fraction remains unchanged

(2x-2 / 1y) (2x + 2 / 1y) - (2x-2 / 1y) ^ 2

(2x-2y1y) (2x + 2y1y) - (2x-2y1y) &;
=[(2x + 1y / 2) - (2x-1y / 2)] (2x-1y / 2)
=Y (2x-1y / 2)
=1y of 2xy-2 & # 178;

If the rank of the coefficient matrix is not equal to the rank of the augmented matrix, then the nonlinear equations have no solution. If there is a solution, the rank of the coefficient matrix is equal to the number of unknowns, then there is a unique solution

① If the rank of the coefficient matrix is not equal to the rank of the augmented matrix, the nonlinear equations have no solution
It is proved that if the system of equations has a solution and the solution is substituted into the original system of equations, then the last column of the augmented matrix is expressed linearly by the column of the coefficient matrix
The rank of the augmented matrix = the rank of the coefficient matrix. So the equations have no solution
② If there is a solution, the rank of the coefficient matrix is equal to the number of unknowns, then there is uniqueness
The number of unknowns is the column number of the coefficient matrix n. The rank of the augmented matrix is also the column number n. the row rank of the augmented matrix is also n
The equations corresponding to the maximum independent group of rows of the augmented matrix are preserved
The rest of the system is a "Cramer" system (the system with coefficient determinant ≠ 0), and the solution is unique

(7x-6xy + 1) - 2 (3x & # 178; - 4xy) - 5, where x = - 1, y = - # 189;, what is the number

It's 7x, isn't it
Original formula = 7x & # 178; - 6xy + 1-6x & # 178; + 8xy-5
=x²+2xy-4
=1+2-4
=-1

Absolute value of B + 1 + (a-b + 1) square = 0, find 2003 of B + 2003 of A

Solution
Is the title right
/b+1/≥0
(a-b+1)²≥0
∴b+1=0
a-b+1=0
∴b=-1,a=-2
∴b^2003+a^2003
=(-1)^2003+(-2)^2003
=-1-2^2003

The following equations are solved by substitution method: {0.7x + 0.5y = 7.5,0.02x-0.01y = 0.19
Seek guidance

X=10
y=1

Li Hua read a story book. On the first day, he read 1 / 4 of the whole book. On the second day, he read the remaining 1 / 5. On the first day, he read 20 more pages than on the second day How many pages is the story book?