K is the slope of the line formed by connecting the points.
Use slope formula:

where the 2 points are the end points of the line (First and last going Left to right)

Substitute into slope formula

You can check if this is correct by going back to graph and going "up 7" and "over 2" to get from one point to the next.
What is the rest of the question
Answer:
x = -1
y = 1
Step-by-step explanation:
<u><em>Since it gives you "y", plug in the number given into the equation:</em></u>
y = -6x - 5
1 = -6x - 5
<u><em>Then, add 5 to both sides:</em></u>
1 = -6x - 5
+5 + 5
________
6 = -6x
<em><u>Divide both sides by -6:</u></em>
6 = -6x
-1 = x
So now you have, x = -1 and y = 1
Answer:

Step-by-step explanation:
If there are 3 milliliters of compound A used for every 4 milliliters of compound B, then we can denote that we use 3x milliliters of compound A and 4x milliliters of compound B to get 533 milliliters of the drug. Thus,

Hence, a chemist must take

of compound B.