"Giving the area, A, as a function of the width" means that we will have the area equation of the rectangle with only w in it and no L. That's ok because we know that the length is 3 more than twice the width, so we have a viable substitution for L in L = 2W + 3. The area for a rectangle is A = L * W, so the equation as a function of the width is A = (2W + 3)(W). Depending upon how far you are to go with this, you could distribute through the parenthesis to simplify this all the way. That would give you
