9514 1404 393
Answer:
 a.  x + 4y = 160
 b.  160
 c.  40
Step-by-step explanation:
a. We can define the variables as ...
 x = number of 1/2-liter bottles
 y = number of 2-liter bottles
For the total number of liters to be 80, we require
 1/2x + 2y = 80
We can multiply this by 2 to eliminate the fraction.
 x + 4y = 160
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b. The x-intercept is 160. It is the number of 1/2-liter bottles required when no 2-liter bottles are used.
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c. The y-intercept is 40. It is the number of 2-liter bottles required when no 1/2-liter bottles are used.