Width of the wall = 3 * length of wrapping roll = 3 * 3.33 = 9.99 ft or
Length of the wall = 2.5 * length of the roll = 2.5 * 3.33 = 8.325 ft
Area of the wall = length * width = 9.99 * 8.325 = 83.16675 sq. ft.
Area of images = 4 * 6 = 24 inch or 0.166667 sq feet.
So the required number of images = 498.99 or 499 (rounded)
So Lara should buy 499 images.