Lena is going to cover her entire garden with topsoil. The garden is 36 feet long by 22 feet wide. A bag of topsoil costs $3 and covers 300 square feet of area.
$9.00 because, 36*22=792 Feet. The reason why it costs $9.00 is because you can't just buy half of the bag, you have to buy the whole thing in this equation.
So, I hope this helped you with this equation because that was really easy.