A certain rectangular window is two times as long as it is wide. If its perimeter is 30 feet, what are its dimensions in terms of length by width? Choose the correct choice from the following answers:
A) 12 by 2  B) 11 by 3  C) 10.5 by 3.5  D) 10 by 5  E) 9 by 3
2x+2y=30   x+y=15   x+2x=15   3x=15   x=5   Answer 10 by 5
<result>D</result>
A certain rectangular window is two times as long as it is wide. If its perimeter is 30 feet, what are its dimensions in terms of length by width?