To solve this problem, we need to determine the expression that represents the total amount Amadou paid, including the 6.75% sales tax.

1. Cost before tax:

   • The total cost of the folders is $0.35f$ (where $f$ is the number of folders).
   • The total cost of the markers is $0.5m$ (where $m$ is the number of markers).
   • So, the total cost before tax is $0.35f + 0.5m$.

2. Sales tax calculation:

   • The sales tax rate is 6.75%, which is equivalent to 0.0675 in decimal form.
   • The tax amount on the total cost is $0.0675 \times (0.35f + 0.5m)$.

3. Total cost including tax:

   • The total amount paid, including the tax, is the original total cost plus the tax amount: $\text{Total cost including tax} = (0.35f + 0.5m) + 0.0675 \times (0.35f + 0.5m)$
   • This can be factored as: $\text{Total cost including tax} = (1 + 0.0675) \times (0.35f + 0.5m) = 1.0675 \times (0.35f + 0.5m)$

So, the correct expression that represents the total amount Amadou paid, including tax, is:

Answer: $\boxed{1.0675(0.35f + 0.5m)}$

Would you like more details or have any questions? Here are some related questions you might find interesting:

1. How would the expression change if the sales tax was different, say 8%?
2. How can you express the sales tax as a separate part of the equation?
3. If Amadou decided to buy twice as many folders, how would that affect the total cost?
4. What would the expression look like if the cost per folder was $0.45 instead of $0.35?
5. How can you derive the expression if Amadou received a discount before applying the tax?

Tip: When working with percentages, always convert them to their decimal form before performing calculations.