The peremiter of a rectangle is 60m. The length is 9 m more than twice the width. Find the demensions?

The perimeter is the sum of all of the sides
  perimeter = length + width + length + width = 2*(length + width)
  perimeter = 2*((9 + 2*width) + width)    (we know length is 9 more than twice width)
  60 = 2*(9 + 3*width)    (combine terms inside parentheses)
  30 = 9 + 3*width    (divide by 2)
  21 = 3*width    (subtract 9)
  7 = width    (divide by 3)

  9 + 2*width = length = 9 + 2*7 = 23

The rectangle is 9 meters wide and 23 meters long.