Question 911748
As practice for linear algebra, topology, differential equations/ all math later in life: THINK GEOMETRICALLY AND DRAW A PICTURE! 
The perimeter of an object is the sum its side lengths or, since a rectangle is symmetrical, 2w+2l. We are given a condition on width and can thus substitute l = w+33 into the perimeter equation. Explicitly, 2w + 2(w+33) = 4w+66. Therefore P =4w+66 which is the required form.