The ratio by weight, measured in pounds, of books to clothes to electronics in a suitcase initially stands at 7:4:3. Someone removes 6 pounds of clothing from the suitcase, thereby doubling the ratio of books to clothes. How many pounds do the electronics in the suitcase weigh? Choose the correct choice from the following choices.
A) 1  B) 3  C) 5  D) 7  E) 9

Rationale: "the weights of the items in the suitcase are 7 k , 4 k , and 3 k . if removing 6 pounds of clothes doubles the ratio of books to clothes , then 6 pounds represents half the weight of the clothes . 2 k = 6 pounds and then k = 3 pounds . the electronics weigh 3 ( 3 ) = 9 pounds . the answer is e ."
Answer: E