When you are painting, tiling, wallpapering or doing anything that involves the region inside a figure, you are dealing with the area of the figure.To calculate the area of a triangle, you can use the formula A = 1/2 base*height. This tells you how many square units it takes to cover the region. Once you know the number of square units, you charge $2 for each square unit, so just multiply, and you've got your answer. So A = 1/2 *4*6 = 12 square units and you'll charge 2*12 = $24 for the job.