Answer: 
Remember: RISE/RUN (y/x). Lines that are increasing have a positive slope, and lines that are decreasing have a negative slope.
You can find the slope in two ways:
1. Useful if the line is graphed: count the units between 2 points on the line.
- Let's use the points (-1, 4) and (4, -4).
- (-1, 4) is 8 units higher than (4, -4) and 5 units to the left of (4, -4).
- Because the line is decreasing, the slope is negative.
- Therefore, the slope is
.
2. Useful if the line is not graphed: find the difference between the y-coordinate values divided by the difference of the x-coordinate values.
- Let's use the points (-1, 4) and (4, -4).

- Therefore, the slope is
.
Answer:
B
Step-by-step explanation:
Not all of the pairs represent the same ratio
X=price of one jumbo popcorn
y=price of one chocolate chip cookies
$5.00=$5.00(100 cts / $)=500 cts
$6.00=$6.00(100 cts / $)=600 cts
We suggest this system of equations:
x+2y=500
x+4y=600
we solve this system of equations by reduction method.
-(x+2y=500)
x+4y=600
----------------------
2y=100 ⇒ y=100/2=50
x+2y=500
x+2(50)=500
x+100=500
x=500-100
x=400
solution: one chocolate chip cookie cost 50 cts.