If the average of 12x and 8y is greater than 200, and x is twice y, what is the least integer value of x ?
Choose the correct option
A) 20
B) 30
C) 40
D) 25
E) 35

Rationale: substitution can be used in the following way : always start with the equation : x = 2 y . it is more straight forward to manage as compared to the inequality . substitute y = x / 2 , not the other way because you need to find the minimum value of x . so you can get rid of y . now go on to the inequality . so 8 y = 8 x / 2 = 4 x now average of 12 x and 4 x is greater than 200 . average of 12 x and 4 x is 8 x . so , 8 x > 200 x > 25 answer : d
Answer: D