I believe it is B, as C and D both are based on the number of books sold while the only variable to determine the amount of money she earns are the additional doors she knocks on.
The equation of direct variation is,

Substitute the values of <em>y</em> and <em>x</em>.

So, the obtained equation will be <em>y</em>=1.35(x).
Let's check with the values of <em>x</em>.
1) If <em>x</em>=4

2) If <em>x</em>=2

3) If <em>x</em>=-2
12 jasjjsisiaiaiiiiiiiiiiii it’s wrong oops
Slope of y=1-2x is -2
Using point intercept form:
y-1=-2(x-3)
y-1=-2x+6
y=-2x+7
Let's Just See How Many Times 30 Goes Into 180

Since 8 trash bags last 30 days, let's multiply

ANSWER
You'll Need 48 Trash Bags For 180 Days