we have
the equation of the line is 
the points are

<u>Method 1</u>
we know that
A relationship between two variables, x, and y, represent a direct variation if it can be expressed in the form
or 
In this problem we have a direct variation
The constant of proportionality k is equal to the slope of the line

so

therefore
<u>the answer is</u>
the slope of the line is equal to

<u>Method 2</u>
we know that
the formula to calculate the slope between two points is equal to

we have

substitute in the formula



therefore
<u>the answer is</u>
the slope of the line is equal to
