Hi,
width of a rectangle is one third its length
Let 3x and x represent the width and length respectively
Question states***
2*x + 2(3x) = 16cm
Solving for x
8x = 16ccm
x = 2cm, the length. the width is 6cm (3*2cm)
CHECKING our Answer***
2*2cmm + 2*6cm = 16cm