sales tax is equal to the price times the sales tax rate
sales tax = price * 5%
= 20 *.05
the total price is equal to the original price plus the sales tax
total price = price + sales tax
this is a parallelogram so you find the total area using base times height.
bh = a
b = 6.5 + 2.5 = 9
h = 6
bh = 9(6)
a = 54 square yards
you now know that the total area is 54 yards. 20 times 3 equals 60 square yards so you know that you need at least 3 bags to cover the whole land area.