360-2x = 8030 △ 3x = 515-6x = 2.4x518-12x = 1.2x5, please solve

360-2x = 8030 △ 3x = 515-6x = 2.4x518-12x = 1.2x5, please solve

360-2x=80
2x=280
x=140
30÷3x=5
3x=6
x=2
15-6x=2.4x5
15-6x=12
6x=3
x=0.5
18-12x=1.2x5
18-12x=6
12x=12
x=1

Fractional equation: (3x + 16 / 4x-7) = 5

（3x+16/4x-7）=5
3x+16=5*(4x-7)
3x+16=20X-35
-17X=-35-16
X=-51/-17
x=3

(3x-1) divided by 3 = 1 - (4x-1) divided by 6

2 (3x-1) = 6 - (4x-1)
Remove bracket: 6x-2 = 6-4x + 1
Merge the same type: 6x-2 = 7-4x
Transfer: 6x + 4x = 7 + 2
Merge the same type: 10x = 9
Change the coefficient of the unknown to 1: x = 0.9

What is the remaining area after cutting a circle with a circumference of 25.12cm on a piece of aluminum with a length of 10cm and a width of 8cm

Radius 25.12 △ 3.14 △ 2 = 4cm
Area 3.14 × 4 square = 50.24 square centimeter
Rectangular area 10 × 8 = 80 square centimeter
The remaining area is 80-50.24 = 29.76 square centimeter

What's the proportion between working hours and total amount of work

The more working hours, the greater the total amount of work

Use a piece of fan-shaped paper with a center angle of 72 degrees and an area of 62.8 square centimeters to roll it into a large cone. The area of the bottom of the cone is______ Square centimeter

62.8 △ 72360 = 314 (square centimeter) the square of the radius of the circle is: 314 △ 3.14 = 100 (square centimeter) 100 = 10 × 10, so the radius is 10 centimeter, 2 × 3.14 × 10 × 72360 = 62.8 × 15 = 12.56 (centimeter) 12.56 △ 3.14 △ 2 = 2 (centimeter) 3.14 × 22 = 3.14 × 4 = 12.56 (square centimeter) answer: the area of the bottom of the cone is 12.56 square centimeter

0.9x-0.3 = 5.1, how to calculate? Finally, we have to check!

0.9x=5.1+0.3
0.9x=5.4
x=5.4/0.9
x=6
Checking calculation: substitute x = 6
0.9*6-0.3=5.4-0.3=5.1
So the answer is right

When a circle is transformed into a rectangle, its perimeter is increased by 4cm and its area is () square centimeter

When a circle is transformed into a rectangle, its perimeter is increased by 4 cm and its area is (12.56) square cm
Radius 4 △ 2 = 2 cm
Area: 3.14 × 2 × 2 = 12.56 square centimeter

Let 4-digit. ABCD satisfy A3 + B3 + C3 + D3 + 1 = 10C + D, then the number of 4-digit is______ ．

A, B, C, D are natural numbers less than 10, ∵ A3 + B3 + C3 + D3 + 1 = 10C + D, ∵ A3 + B3 + C3 + D3 + 1 is a two digit number, ∵ a, B, C, D are natural numbers less than 5, ∵ if C = 1, d = 0, then a = 2, B = 0, then the four digit number is 2010, if C = 1, d = 1, then a = 2, B = 0

The radius of the sector is 10, the center angle is 120 ° and the height of the rolled cone is what?
I calculate 20 / 3 times root 2, the answer is 5 times root 3, why!

Is the answer to the wrong, I calculated out is 20 / 3 times root 2!