the perimeter of a rectangle is 64 meters, the length is 8 meters longer than the width. what are the dimensions?

P=2(l+w) 
so 
2(l+w)=64 or l=32-w 
and we also can say 
l=w+8 

setting them equal 
w+8=32-w 
2w=32-8 
2w=24 
w=12 
and so l=20 

:)