similar shapes have proportional sides so divide 18/27 to get the proportion then multiply each side of the smaller polygon by the proportion to get the sides for the larger polygon and add the larger polygons sides together.
If the total sales are $23152.81 and the sales tax is 5%, take the total sales divided by 1.05 $23152.81/1.05 = $22050.30 (gaves you the sales) to get the sales tax, subtract the total sales from the sales= Sales are $22050.30Tax is $1102.51 hope this helps :)