math
posted by Anonymous .
Alan built an additional room onto his house. the length of the room is 3 times the width. the perimeter of he room is 60 feet. What is the length of the room?
a 7.5 feet
b 22.5 feet

sorry the all options are:
a 7.5 feet
b 22.5 feet
c 15 feet
d 45 feet....
plz explain how to do also. plz . thanks 
Perimeter is 2L + 2W
L=3W
Perimeter=6W+2W
I assume you can take if from here. 
sorry but i don't get it. can u help? :(

solve for Width in that last equation, then multiply it by 3 to get the length.