20 feet of lumber cost $138.40. what is the cost per foot

$6.92

Step-by-step explanation: Whenever you see the word per in a math problem, that means division. So right now, you could set up an equation that looks like this. 20L=130.40 (let L mean cost per foot of lumber). If you want to find the cost per foot you need have 1L or just L on one side of the equation. Well, the easiest way to do that would be to divide by 20 on both sides. And that would get you L= 6.92. And since L means the cost per foot of lumber, that cost would be $6.92. Hope this helps!

for this case we have by definition, if two lines are perpendicular, then the product of their slopes is -1.

then, given the following line:

so,

we are looking for m_ {2}:

then, the line is given by:

we find "b" replacing the given point:

finally, the equation is:

option c