Why is the addition of any number plus 9 equal to the addition of that number

Why is the addition of any number plus 9 equal to the addition of that number

10-1=9
Any number plus nine is ten plus one and one minus one,
So you add it up

-1, - 2, - 3, - 4, - 5, 2, 3, 6, 9, 10 every four add up to a number
On the five corners of the five pointed star and the intersection of every two lines, fill in a number so that their sum is equal to the same number

Because it is not easy to describe, the upright Pentagram is regarded as five elements, the first line is 6, its lower 2, - 1, - 5,10, then lower - 2, - 4, then lower - 3, the lowest 3,9, and all are 6

The sum of the five digits in the number from 1 to 35 is 97. I'll give him all the points that can help me,
If any five digits from 1 to 35 add up to 97, I will give him the most complete score
The third floor is opportunistic. It's absolutely not worth it

15+19+20+21+22=97
1+35+2+34+25=97
3+33+4+31+26=97
5+6+32+30+24=97
7+16+29+18+27=97

Eight numbers from 1 to 8 are divided into two intersecting big circles. Each big circle has five numbers and the sum is equal to 21

There are two numbers in the intersection of the great circle, and the sum of them is 21 * 2 - (1 + 2 + 3 +. + 8) = 6, and the rest is filled with three numbers, and the sum of them is 15,
The first circle 2 6 7 1 5
The second 3 8 4 1 5

1 2 3 4 5 6 7 8 fill in eight circles so that the sum of five numbers on two adjacent circles is equal to 21
Eight circles make up two circles with two numbers in common.

1,8,6,2,4
3,5,7,2,4

Fill the numbers 1-8 in the circle in the figure below, so that the sum of the five numbers on the two Pentagon is equal to 21

Observation number: 1, 2, 3, 4, 5, 6, 7, 8, from small to large, the meaning of the title makes the sum of five numbers on two pentagons equal to 21, 7 and 8 can not be together, assuming that 8 is on the right side of the Pentagon, according to the principle of combining large numbers and decimals, 8 and 1 are on one side, so 1 is on the right side, and the right side is still 12

If we put 1,2,3,4,5,6,7,8. In eight cycles, how can we make the result of every five cycles equal to 21, in which there are two cycles

12378
twelve thousand four hundred and sixty-eight
twelve thousand five hundred and sixty-seven
thirteen thousand four hundred and sixty-seven
twenty-three thousand four hundred and fifty-seven
All of the above five groups were 21

Which six of the numbers 4,5,6,7,9,10,14,16,17,19,20,23,24,27,28,31,32 add up to 107?

14+17+19+31+32+5=107
4+16+17+10+32+28=107
27+23+14+16+20+7=107
19+31+20+14+16+7=107
19+31+10+24+16+7=107
That's all I think about

How many squares and triangles are each

The square is three and the triangle is seven
3 * 7 * 37 = 777 (* is a multiplication sign)

9.9x9.9 plus 1.99 is equal to?

100