It is given in the question that a rectangle is 3 times as long as it is wide. the perimeter is 60 cm.
Let the width of the rectangle be x cm. And length is 3 times of width, therefore length is 3x cm .
And perimeter is the sum of all sides. That is


Dividing both sides by 8,

Therefore width is 7.5 cm and length is 3 times of it, that is length is 22.5 cm .