What is a length and width of 30 perimeter

The perimeter is two times the length plus two times the width.

Let width = x

Let length = 3x

Perimeter = 30

2x + 2 (3x) = 30

2x + 6x = 30

8x = 30

x = 3.75

Substitute this value of x into the length and width to obtain your dimensions.