Li Ming went to the stationery store to buy pencils and erasers for 30 students in the school's art group. It is known that each pencil costs m yuan, and each eraser costs n yuan For two pencils and three erasers, the total payment is RMB

Li Ming went to the stationery store to buy pencils and erasers for 30 students in the school's art group. It is known that each pencil costs m yuan, and each eraser costs n yuan For two pencils and three erasers, the total payment is RMB

A: 30 (2m + 3n)~~~

The stationery store brought in 8 boxes of watercolor pens and 6 boxes of rubbers. It costs 4 yuan less to buy watercolor pens than to buy rubbers. Each box of watercolor pens costs 8.5 yuan. How much is each box of rubbers?

This problem can solve the equation
Set X yuan per box of rubber
6X-4=8*8.5
X=12
You can also use the formula
【（8.5*8）+4】|6=12
A:

A rectangular playground, 124 meters long and 108 meters wide, is planted with saplings at four corners and around to make the distance between two adjacent saplings equal,
How many meters apart is the farthest distance? How many seedlings are needed? The formula is needed

The greatest common divisor of 124 and 108 is 4, so plant one tree at a distance of four meters
Length: 124 △ 4 = 31 (trees) width: 108 △ 4 = 27 (trees)
A total of (31 + 27) × 2 = 116 (trees)

What does peacock's tail look like? What does rabbit's eyes look like? What does deer's horn look like? What does white goose's forehead look like?

The peacock's tail is like a colorful fan,
The rabbit's eyes are like a red lantern,
The deer's horns are like two branches,
The forehead of the white goose is like the head of the longevity man

Calculation: (1) / (x-3) / (x + 2) / (x ^ 2-9) - (1) / (x ^ 2 + 5x + 6)

1/(x-3)÷(x+2)/(x^2-9)-1/(x^2+5x+6)
=1/(x-3)÷(x+2)/[(x-3)(x+3)]-1/(x+2)(x+3)
=1/(x-3)*(x-3)(x+3)/(x+2)-1/(x+2)(x+3)
=(x+3)/(x+2)-[1/(x+2)-1/(x+3)]
=(x+3)/(x+2)-1/(x+2)+1/(x+3)
=(x+3-1)/(x+2)+1/(x+3)
=1+1/(x+3)
=(x+3+1)/(x+3)
=(x+4)/(x+3)

The basketball court is 28m long and 15m wide. How to draw its plan (only draw the boundary) with a scale of 1:500?
1: What's the proportion of 500? Is it 28 cm long?
What kind of design

28 m = 2800 cm, 15 m = 1500 cm
2800 × 1 / 500 = 5.6CM 1500 × 1 / 500 = 3cm
Just draw a plan of this length and width

(1) Square of (- 2A + 1) = ()
(2) Square of (- 2a-1) = ()
(3) The square of (2x-y) = the square of 4x + () the square of XY + y
（4）（-a+b)(a-b)=()

(1) Square of (- 2A + 1) = (4a & sup2; - 4A + 1)
(2) Square of (- 2a-1) = (4a & sup2; + 4A + 1)
(3) Square of (2x-y) = square of 4x + (- 4) XY + square of Y
（4）（-a+b)(a-b)=(-a²+2ab-b²)

How to change kilogram into meter for knitted fabric?

1 / g weight / full width
For example, the gram weight is 140gsm, and the whole door width is 160cm
1 / 0.14 / 1.60 = 4.46M

How to divide an isosceles trapezoid into four shapes with the same size?
It's better to have a picture,

As shown in the picture,
\First make ef / / BC, make AE + DF = FC, then make vertical line, make Ag = Ge, BM = FN!

It's a semicircle from the left and the front, and a circle from the top. What's the three-dimensional figure?

It's a hemisphere