Answer:
I do not have access to the specific details of Laura's purchase, such as the quantity of topsoil she will buy or how much of it she plans to use. Therefore, I cannot determine the percentage of topsoil that Laura will not use.
However, if we assume that Laura buys a certain amount of topsoil but only uses a portion of it, we can calculate the percentage of topsoil that she does not use by dividing the amount she does not use by the total amount she bought and then multiplying by 100.
For example, if Laura buys 10 cubic meters of topsoil but only uses 8 cubic meters, the percentage of topsoil that she does not use would be:
[(10 - 8) / 10] x 100 = 20%
So in this scenario, 20% of the topsoil that Laura bought would not be used.