18-6x_<0 inequation

Given the inequality:
$$18 - 6 x \leq 0$$
To solve this inequality, we must first solve the corresponding equation:
$$18 - 6 x = 0$$
Solve:
Given the linear equation:

18-6*x = 0

Move free summands (without x)
from left part to right part, we given:
$$- 6 x = -18$$
Divide both parts of the equation by -6

x = -18 / (-6)

$$x_{1} = 3$$
$$x_{1} = 3$$
This roots
$$x_{1} = 3$$
is the points with change the sign of the inequality expression.
First define with the sign to the leftmost point:
$$x_{0} \leq x_{1}$$
For example, let's take the point
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$- \frac{1}{10} + 3$$
=
$$\frac{29}{10}$$
substitute to the expression
$$18 - 6 x \leq 0$$
$$18 - \frac{6 \cdot 29}{10} \leq 0$$

3/5 <= 0

but

3/5 >= 0

Then
$$x \leq 3$$
no execute
the solution of our inequality is:
$$x \geq 3$$

         _____  
        /
-------•-------
       x1