A. they sold the least lemonade with the recipe that used 3 lemons
b. they sold the least lemonade with the recipe that used 7 lemons
c. they sold the most lemonade with the recipe that used 3 lemons
d. they sold the most lemonade with the recipe that used 7 lemons

B. They sold the least lemonade with the recipe that used 7 lemons

Step-by-step explanation:

B. They sold the least lemonade with the recipe that used 7 lemons

Step-by-step explanation:

As can be seen from the graph the points are

(3, 37)

This means that when they used 3 lemons then they sold around 37 cups

(4, 32)

This means that when they used 4 lemons then they sold around 32 cups

(5, 40)

This means that when they used 5 lemons then they sold around 40 cups

(6, 35)

This means that when they used 6 lemons then they sold around 40 cups

(7, 26)

This means that when they used 7 lemons then they sold around 26 cups

It can be seen that the last case is when they sold the least number of cups.

5.

x + 2(x + 1) = 8 --> x = 2

y = 2 + 1 = 3

7.

3(9 + 2y) + 5y = 20 --> y = -7/11

x = 9 + 2(-7/11) = 85/11

9.

3(-1 - 2y) + 5y = -1 --> y = -2

x = -1 - 2(-2) = 3