Many Test Takers would approach this with a combination of algebra and geometry rules, which is fine - the math is easy enough to do. On Test Day though, you have 2 goals when dealing with a question:
1) Get it correct, if possible.
2) Answer it in the fastest way possible.
Since the answer choices ARE numbers, and the prompt describes some rather specific facts, you can use the answers to your advantage and TEST THE ANSWERS.
We're told 2 things about a rectangle:
1) It's length is TWICE it's width.
2) It's perimeter is 10
We're asked for the dimensions of the rectangle.
Looking at the answer choices, there are some really easy answers to knock out....
Answer C: 2 by 4......this perimeter would = 12, not 10. ELIMINATE C.
Answer D: 3 by 6......this perimeter would = 18, not 10. ELIMINATE D.
Answer E: 10/3 by 20/3......this perimeter would be > 18, not 10. ELIMINATE E.
With the remaining 2 answers, only 1 of them has a length that is TWICE the width....
Answer A: 3/2 and 7/2.....7/2 is NOT TWICE 3/2. Eliminate A.
GMAT assassins aren't born, they're made,