Problem: a rectangular window is twice as long as it is wide . if its perimeter is 18 feet , then what are its dimensions in feet ? 
Options: ['a ) 3 / 2 by 7 / 2', 'b ) 5 / 3 by 10 / 3', 'c ) 2 by 4', 'd ) 3 by 6', 'e ) 10 / 3 by 20 / 3']
d