For example, "when he climbed to the middle of the ladder 1 level", there were x levels up and down.

Then: this ladder * * * has x+ 1+x grade.

When he climbed to the middle of the 1 horizontal ladder.

He went down three floors.

x-3 x+3

He climbed seven more floors.

x-3+7 x+3-7

He went back two grades.

x-3+7-2 x+3-7+2

He climbed eight more steps, and there was still 1 step from the top of the ladder.

x-3+7-2+8 x+3-7+2-8

At this point, there are 1 levels from the top of the ladder:

x+3-7+2-8= 1

x= 1 1

This ladder * * * has x+ 1+x=23 levels.

number axis

Is a specific geometric figure. A straight line is a collection of countless points, and there are countless real numbers including positive real numbers, zero real numbers and negative real numbers. Because of their * * * nature, they use countless points on a straight line to represent real numbers. At this time, a straight line with origin, positive direction and unit length is used to represent real numbers. When the right side is defined as the positive direction, the number represented by the upper point on the right side of two numbers on this straight line is always greater than the number represented by the upper point on the left side, positive numbers are greater than zero, and zero is greater than negative numbers.