Answer:
The missing value is 12
Step-by-step explanation:
In a proportional relationship the ratios of the two variables are equivalent. That is, if one variable doubles, the other will double in the same way. Using the values:
X 8 16 24
Y 6 ? 18
When X is doubled from 8 to 16, 6 must be doubled from 6 to 12
When X is 3 times 8 = 24, Y is 3 times 6 = 18
Thus, the missing value is 12