In the morning, marco sold 12 cups of lemonade for $3. by the end of the day, he had earned $9. how many cups of lemonade did he sell in all?

Kaycee did not keep lemonade and dollars in corresponding positions in the ratios of the proportion. The proportion should be 12/3=c/9 or it could be written 3/12=9/c. Dollars should be in the same position and cups should be in the same position across ratios.

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional